{"id":316,"date":"2022-06-17T15:22:42","date_gmt":"2022-06-17T15:22:42","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/alphamodule\/?post_type=chapter&#038;p=316"},"modified":"2022-06-17T15:23:26","modified_gmt":"2022-06-17T15:23:26","slug":"advanced-experimental-design-learn-it-1","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/alphamodule\/chapter\/advanced-experimental-design-learn-it-1\/","title":{"raw":"Advanced Experimental Design: Learn It 1","rendered":"Advanced Experimental Design: Learn It 1"},"content":{"raw":"<div class=\"textbox learning-objectives\">\r\n<h3>learning GOALS<\/h3>\r\n<ul>\r\n \t<li>Determine whether or not an experiment has been designed well.<\/li>\r\n \t<li>Use a diagram to illustrate the design of a given experiment.<\/li>\r\n \t<li>Determine factors, other than the factor of interest, that could have an effect on the response variable of a given experiment (nuisance factors).<\/li>\r\n \t<li>Identify blocks in a specified experiment.<\/li>\r\n<\/ul>\r\n<\/div>\r\nIn the next activity, you will need to identify the basic principles of type of experimental design called the completely randomized block design. You'll also need to and describe the role blocking plays and how to use a completely randomized block design to achieve a research objective.\r\n<h2>Randomized Design<\/h2>\r\nIn previous activities, you learned that the design of an experiment can have a major impact on its results. If an experiment is not designed well, its results may be meaningless and misleading.\r\n<h3>Good Experimental Design<\/h3>\r\nIn Questions 1 - 3 below, you'll consider a large and important study as your deepen your understanding of the key components of an experiment, and pick up some new terms. Recall the key components of experimental design you learned about in section\u00a0<em>[2C]<\/em>: factor of interest, response factor, nuisance factors, treatments, and random assignment. Can you describe what role each of these plays in an experiment?\r\n<div class=\"textbox examples\">\r\n<h3>Recall<\/h3>\r\nCore skill:\r\n[reveal-answer q=\"16865\"]Describe the key components of experimental design[\/reveal-answer]\r\n[hidden-answer a=\"16865\"]\r\n<ul>\r\n \t<li><strong>Factor of Interest:<\/strong> the explanatory variable (independent variable), which is what we suspect has an effect on the response variable.<\/li>\r\n \t<li><strong>Response Factor:<\/strong> the dependent variable, which we suspect is affected by the factor of interest.<\/li>\r\n \t<li><strong>Nuisance Factors<\/strong>: these are not of interest in the study but may have an effect on the response variable.<\/li>\r\n \t<li><strong>Treatments:<\/strong> experimental conditions into which the participants are divided, some into the a group receiving the treatment of interest and others into a control group that does not receive the treatment.<\/li>\r\n \t<li><strong>Random Assignment:\u00a0<\/strong>the process of using random selection to assign participants into the treatment groups.<\/li>\r\n<\/ul>\r\nRefer to section\u00a0<em>2C: Experimental Design\u00a0<\/em>for more details as needed.\r\n\r\n[\/hidden-answer]\r\n\r\n<\/div>\r\nRecall that researchers conduct experiments by assigning subjects (sometimes called experimental units) to certain experimental conditions or treatments (also called levels of the factor of interest) and then observing outcomes on the response variable.\u00a0<span style=\"font-size: 1em;\">One experimental condition is the treatment of interest -- this is what the researcher changes or manipulates to see if it causes a change in the response variable.\u00a0<\/span><span style=\"font-size: 1em;\">You learned that the other group is called the\u00a0control group. The control group does not receive the treatment of interest and is usually kept under conditions considered typical or common.\u00a0 The control group is essential to the experiment. It shows that, all else being equal, the factor of interest is either making a change in the response variable or it isn't. There are some particular techniques that researchers use to make sure all the treatment groups are indeed otherwise equivalent.\u00a0<\/span>\r\n<ul>\r\n \t<li>A <strong>placebo<\/strong> is a type of control treatment. A placebo is a harmless version of the treatment that does not contain any active ingredients (e.g., a sugar pill). It will typically look, taste, and smell like the treatment of interest or mimic it so that the two treatments appear identical to the subjects; this way the subjects don\u2019t know which treatment they are receiving. A phenomenon called the\u00a0<strong>placebo effect\u00a0<\/strong>can sometimes, though, introduce ambiguity in the assessment of any changes occurring in the response variable. You'll read more about the use of a placebo and the placebo effect in Question 1 below.<\/li>\r\n \t<li>Researchers will use a technique called\u00a0<strong>blinding,\u00a0<\/strong>in which the subjects do not know which treatment they received. A\u00a0<strong>double-blind\u00a0<\/strong>study is one in which neither the subject nor the people collecting data on the subjects know about the treatment assignments. Other blinding levels exist as well, especially in medical drug trials, including ones in which only the top level directors of a study have information about which treatment the patient receives. The patients, data collectors, and even the patients' doctors and the people analyzing the data don't know who received the treatment and who got the placebo.<\/li>\r\n<\/ul>\r\nLook for the terms\u00a0<em>placebo, placebo effect, blind, and double-blind <\/em>in the questions and examples below.\r\n<div class=\"textbox tryit\">\r\n<h3>Video Placement<\/h3>\r\n<span style=\"background-color: #e6daf7;\">[Perspective Video: A summary of the key components: factors (interest, response, nuisance), treatments (experimental, control, placebo, placebo effect), treatments (aka levels[and why \"levels\"? e.g. different dosages of a drug], random assignment, blinding, double-blinding) -- it would be beneficial to include a diagram like the one in Question 3]<\/span>\r\n\r\n<\/div>\r\n<span style=\"background-color: #ffff99;\">[A choose-your-study example could be placed here to mimic Question 1 - 3]<\/span>\r\n\r\nNow it's your turn to explore a large and influential experiment as you answer Questions 1 - 3. Keep your eye out for the key components and terms you'll seen so far.\r\n<div class=\"textbox key-takeaways\">\r\n<h3>Question 1<\/h3>\r\nIn the 1950\u2019s, a large-scale experiment was designed to test the effectiveness of the Salk vaccine in preventing polio, which had killed or paralyzed thousands of children. Children were placed in either the experimental or control group through a process of random assignment. Suppose that [latex]200,745[\/latex] children were given a treatment consisting of Salk vaccine injections, while a control group of [latex]201,229[\/latex] children were injected with a placebo that contained no drug. The children being injected did not know whether they were getting the Salk vaccine or the placebo. Among the children given the Salk vaccine, [latex]33[\/latex] later developed paralytic polio, but among the children given the placebo, [latex]115[\/latex] later developed paralytic polio.\r\n\r\nPart A: A good experiment always starts with a good research question. What is the research objective or question in this experiment?\r\n\r\n[reveal-answer q=\"891968\"]Hint[\/reveal-answer]\r\n[hidden-answer a=\"891968\"]A researcher must determine the question(s) they want answered. The question(s) must clearly identify the groups to be studied. The question is usually about whether one thing causes another.[\/hidden-answer]\r\n\r\n&nbsp;\r\n\r\nPart B: What is the factor of interest in this experiment? What is the response variable in this experiment?\r\n\r\n[reveal-answer q=\"12573\"]Hint[\/reveal-answer]\r\n[hidden-answer a=\"12573\"]Remember the factor of interest (also known as the independent variable or the explanatory variable) is the factor that the researcher purposely changes to see if it causes a specific outcome. The response variable (also known as the response factor or dependent variable) is the factor that is expected to change and will be measured at the end of the experiment.[\/hidden-answer]\r\n\r\n&nbsp;\r\n\r\nPart C: In an experiment, subjects are often referred to as experimental units. This name emphasizes that the objects measured do not have to be human beings. They could, for example, be government buildings, department stores, animals, or computer chips. When people are the experimental units, we call them subjects, participants, or patients, depending upon the context of the study. What are the experimental units in this experiment?\r\n\r\n[reveal-answer q=\"526914\"]Hint[\/reveal-answer]\r\n[hidden-answer a=\"526914\"]Remember, the experimental units are the subjects of the experiment.[\/hidden-answer]\r\n\r\n&nbsp;\r\n\r\nPart D: What are the treatments or levels of the factor of interest?\r\n\r\n[reveal-answer q=\"761629\"]Hint[\/reveal-answer]\r\n[hidden-answer a=\"761629\"]Remember, the treatments, also known as levels of the factor of interest, are imposed by the researcher on the groups.[\/hidden-answer]\r\n\r\n&nbsp;\r\n\r\nAn experiment will compare the recorded values of the response variable across multiple levels of the factor of interest. Often this includes the treatment of interest, but it should also have a second baseline level treatment for comparison to help with analyzing the effectiveness. The experimental units are split into two groups\u2014one group receives the treatment of interest (this is usually called the experimental group) and the other group does not. The group that does not receive the treatment of interest is the control group.\r\n\r\n&nbsp;\r\n\r\nPart E: Identify the experimental units that are in the experimental group and the experimental units that are in the control group.\r\n\r\n[reveal-answer q=\"216422\"]Hint[\/reveal-answer]\r\n[hidden-answer a=\"216422\"]Remember the experimental group consists of the experimental units that will receive the treatment of interest. The control group consists of the experimental units that will receive the placebo.[\/hidden-answer]\r\n\r\n&nbsp;\r\n\r\nA second method of defining the control group is through the use of a placebo. The <strong>placebo effect<\/strong> is a positive response that people who believe they are receiving treatment for a condition have, even if what they are actually receiving is a placebo. It is a fascinating connection between mind and body that is still not completely understood. The placebo effect can make it difficult to gauge the effects on the response variable.\r\n\r\n&nbsp;\r\n\r\nPart F: Why is it important to use a placebo in this study?\r\n\r\n[reveal-answer q=\"830533\"]Hint[\/reveal-answer]\r\n[hidden-answer a=\"830533\"]What do <em>you<\/em> think?[\/hidden-answer]\r\n\r\n&nbsp;\r\n\r\nIn medicine, the randomized experiment (clinical trial) has become the gold standard for the evaluation of new medical treatments because of its effectiveness and ability to objectively support conclusions. The Cochrane Collaboration is an organization devoted to synthesizing evidence from medical studies all over the world. According to this organization, there have been hundreds of thousands of randomized experiments comparing medical treatments. In most countries, a company can\u2019t get a new drug approved for sale unless it has been tested in a well-designed experiment. A good experiment will randomly assign the experimental units to the treatments.\r\n\r\n&nbsp;\r\n\r\nPart G: Why is <strong>random assignment<\/strong> important?\r\n\r\n[reveal-answer q=\"102593\"]Hint[\/reveal-answer]\r\n[hidden-answer a=\"102593\"]Refer to your notes on experimental design.[\/hidden-answer]\r\n\r\nIn an experiment, it is important that each group be treated the same way. It is also important that the subjects do not adjust their behavior because of the treatment they are receiving. For this reason, many experiments use a technique called blinding. <strong>Blinding<\/strong> refers to nondisclosure of the treatment an experimental unit is receiving. Whoever has contact with the subjects during the experiment, including the data collectors who record the experimental units\u2019 response outcomes, should be blind to the treatment information. When neither the subject nor those having contact with the subject know the treatment assignment, the study is called <strong>double-blind<\/strong>.\r\n\r\n&nbsp;\r\n\r\n<span style=\"font-size: 1rem; text-align: initial;\">Part H: Why do you think blinding is important? Would it be more ideal for a study to be a blind or double-blind study? Was blinding or double-blinding used in the experiment involving the Salk vaccine?<\/span>\r\n\r\n[reveal-answer q=\"922260\"]Hint[\/reveal-answer]\r\n[hidden-answer a=\"922260\"]What do <em>you<\/em> think?[\/hidden-answer]\r\n\r\n&nbsp;\r\n\r\nPart I: Replication of studies increases confidence in the conclusion. Was replication achieved in the experiment involving the Salk vaccine? Explain.\r\n\r\n[reveal-answer q=\"717481\"]Hint[\/reveal-answer]\r\n[hidden-answer a=\"717481\"]Replication helps to ensure that the results of an experiment are truly caused by the change in the factor of interest and not by other hidden factors or natural variation in data. A well-designed experiment always achieves replication by including large numbers of participants. Replication can also be achieved by repeating the entire experiment with new groups of participants.[\/hidden-answer]\r\n\r\n<\/div>\r\nNow, compile a list of the key components that you identified in Question 1. Use them to answer Question 2.\r\n<div class=\"textbox key-takeaways\">\r\n<h3>question 2<\/h3>\r\nIn Question 1, you identified the key components that make up a well-designed experiment in Parts C, D, E, G, H, and I. Review them and use them to answer Part A below.\r\n\r\n&nbsp;\r\n\r\nPart A: List the components that should be included in a well-designed experiment.\r\n\r\n[reveal-answer q=\"557332\"]Hint[\/reveal-answer]\r\n[hidden-answer a=\"557332\"]Review your answers to Question 1 Parts C, D, E, G, H, and I.[\/hidden-answer]\r\n\r\n&nbsp;\r\n\r\nPart B: Do you believe the experiment in Question 1 involving the Salk vaccine is an experiment that was designed well? Explain.\r\n\r\n[reveal-answer q=\"820585\"]Hint[\/reveal-answer]\r\n[hidden-answer a=\"820585\"]What do <em>you<\/em> think? Use the key components you identified to support your answer.[\/hidden-answer]\r\n\r\n&nbsp;\r\n\r\nPart C: Would you trust any conclusions drawn from this experiment or would you be skeptical? Explain.\r\n\r\n[reveal-answer q=\"484529\"]Hint[\/reveal-answer]\r\n[hidden-answer a=\"484529\"]What do you think? Did the experiment include the key components necessary for a well-designed experiment? [\/hidden-answer]\r\n\r\n<\/div>\r\nIn Question 3, you'll fill in the blanks to describe how many participants were assigned into each group and what was compared at the end of the experiment so that conclusions might be drawn.\r\n<div class=\"textbox key-takeaways\">\r\n<h3>question 3<\/h3>\r\n3) Complete the diagram below to illustrate the design of the Salk vaccine experiment.\r\n\r\n<img class=\"alignnone wp-image-1124\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/5738\/2022\/01\/12010705\/Screen-Shot-2022-01-11-at-5.06.10-PM-300x100.png\" alt=\"A flowchart. The first box reads &quot;Experimental units: 401,974 subjects.&quot; It has two arrows coming out of it, both arrows are labeled &quot;randomly assigned.&quot; One of the arrows goes to a box with text reading &quot;Experimental Group&quot; and the other to another box reading &quot;Control Group.&quot; Both of these have arrows leading to another box that has nothing written in it.\" width=\"1098\" height=\"366\" \/>\r\n\r\n[reveal-answer q=\"723903\"]Hint[\/reveal-answer]\r\n[hidden-answer a=\"723903\"]How many participants were included in each group? What was compared at the end of the experiment?[\/hidden-answer]\r\n\r\n<\/div>\r\nThe Salk vaccine experiment was one of the largest health experiments ever conducted. It was an experiment because subjects were given treatments, but it's not always possible to conduct experiments. Ethical issues, cost, time, and other considerations sometimes prohibit the use of an experiment. For example, it would be unethical to conduct an experiment on the effects of texting while driving with two treatment groups: those who text while driving and those who don't. We would need to request half the subjects to engage in a behavior that we already suspect might cause injury or fatality. In this case, an observational study would be more appropriate, in which previously recorded vehicle collision data is observed to understand the effects of texting while driving.\r\n\r\nThe Salk Vaccine experiment used a <strong>completely randomized design<\/strong> because the experimental units (subjects) were randomly assigned to one of two (or more) treatments. Another type of experimental design called block design, or blocking, can be added to a completely randomized design to strengthen the results. Let's explore this type of design now.","rendered":"<div class=\"textbox learning-objectives\">\n<h3>learning GOALS<\/h3>\n<ul>\n<li>Determine whether or not an experiment has been designed well.<\/li>\n<li>Use a diagram to illustrate the design of a given experiment.<\/li>\n<li>Determine factors, other than the factor of interest, that could have an effect on the response variable of a given experiment (nuisance factors).<\/li>\n<li>Identify blocks in a specified experiment.<\/li>\n<\/ul>\n<\/div>\n<p>In the next activity, you will need to identify the basic principles of type of experimental design called the completely randomized block design. You&#8217;ll also need to and describe the role blocking plays and how to use a completely randomized block design to achieve a research objective.<\/p>\n<h2>Randomized Design<\/h2>\n<p>In previous activities, you learned that the design of an experiment can have a major impact on its results. If an experiment is not designed well, its results may be meaningless and misleading.<\/p>\n<h3>Good Experimental Design<\/h3>\n<p>In Questions 1 &#8211; 3 below, you&#8217;ll consider a large and important study as your deepen your understanding of the key components of an experiment, and pick up some new terms. Recall the key components of experimental design you learned about in section\u00a0<em>[2C]<\/em>: factor of interest, response factor, nuisance factors, treatments, and random assignment. Can you describe what role each of these plays in an experiment?<\/p>\n<div class=\"textbox examples\">\n<h3>Recall<\/h3>\n<p>Core skill:<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q16865\">Describe the key components of experimental design<\/span><\/p>\n<div id=\"q16865\" class=\"hidden-answer\" style=\"display: none\">\n<ul>\n<li><strong>Factor of Interest:<\/strong> the explanatory variable (independent variable), which is what we suspect has an effect on the response variable.<\/li>\n<li><strong>Response Factor:<\/strong> the dependent variable, which we suspect is affected by the factor of interest.<\/li>\n<li><strong>Nuisance Factors<\/strong>: these are not of interest in the study but may have an effect on the response variable.<\/li>\n<li><strong>Treatments:<\/strong> experimental conditions into which the participants are divided, some into the a group receiving the treatment of interest and others into a control group that does not receive the treatment.<\/li>\n<li><strong>Random Assignment:\u00a0<\/strong>the process of using random selection to assign participants into the treatment groups.<\/li>\n<\/ul>\n<p>Refer to section\u00a0<em>2C: Experimental Design\u00a0<\/em>for more details as needed.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<p>Recall that researchers conduct experiments by assigning subjects (sometimes called experimental units) to certain experimental conditions or treatments (also called levels of the factor of interest) and then observing outcomes on the response variable.\u00a0<span style=\"font-size: 1em;\">One experimental condition is the treatment of interest &#8212; this is what the researcher changes or manipulates to see if it causes a change in the response variable.\u00a0<\/span><span style=\"font-size: 1em;\">You learned that the other group is called the\u00a0control group. The control group does not receive the treatment of interest and is usually kept under conditions considered typical or common.\u00a0 The control group is essential to the experiment. It shows that, all else being equal, the factor of interest is either making a change in the response variable or it isn&#8217;t. There are some particular techniques that researchers use to make sure all the treatment groups are indeed otherwise equivalent.\u00a0<\/span><\/p>\n<ul>\n<li>A <strong>placebo<\/strong> is a type of control treatment. A placebo is a harmless version of the treatment that does not contain any active ingredients (e.g., a sugar pill). It will typically look, taste, and smell like the treatment of interest or mimic it so that the two treatments appear identical to the subjects; this way the subjects don\u2019t know which treatment they are receiving. A phenomenon called the\u00a0<strong>placebo effect\u00a0<\/strong>can sometimes, though, introduce ambiguity in the assessment of any changes occurring in the response variable. You&#8217;ll read more about the use of a placebo and the placebo effect in Question 1 below.<\/li>\n<li>Researchers will use a technique called\u00a0<strong>blinding,\u00a0<\/strong>in which the subjects do not know which treatment they received. A\u00a0<strong>double-blind\u00a0<\/strong>study is one in which neither the subject nor the people collecting data on the subjects know about the treatment assignments. Other blinding levels exist as well, especially in medical drug trials, including ones in which only the top level directors of a study have information about which treatment the patient receives. The patients, data collectors, and even the patients&#8217; doctors and the people analyzing the data don&#8217;t know who received the treatment and who got the placebo.<\/li>\n<\/ul>\n<p>Look for the terms\u00a0<em>placebo, placebo effect, blind, and double-blind <\/em>in the questions and examples below.<\/p>\n<div class=\"textbox tryit\">\n<h3>Video Placement<\/h3>\n<p><span style=\"background-color: #e6daf7;\">[Perspective Video: A summary of the key components: factors (interest, response, nuisance), treatments (experimental, control, placebo, placebo effect), treatments (aka levels[and why &#8220;levels&#8221;? e.g. different dosages of a drug], random assignment, blinding, double-blinding) &#8212; it would be beneficial to include a diagram like the one in Question 3]<\/span><\/p>\n<\/div>\n<p><span style=\"background-color: #ffff99;\">[A choose-your-study example could be placed here to mimic Question 1 &#8211; 3]<\/span><\/p>\n<p>Now it&#8217;s your turn to explore a large and influential experiment as you answer Questions 1 &#8211; 3. Keep your eye out for the key components and terms you&#8217;ll seen so far.<\/p>\n<div class=\"textbox key-takeaways\">\n<h3>Question 1<\/h3>\n<p>In the 1950\u2019s, a large-scale experiment was designed to test the effectiveness of the Salk vaccine in preventing polio, which had killed or paralyzed thousands of children. Children were placed in either the experimental or control group through a process of random assignment. Suppose that [latex]200,745[\/latex] children were given a treatment consisting of Salk vaccine injections, while a control group of [latex]201,229[\/latex] children were injected with a placebo that contained no drug. The children being injected did not know whether they were getting the Salk vaccine or the placebo. Among the children given the Salk vaccine, [latex]33[\/latex] later developed paralytic polio, but among the children given the placebo, [latex]115[\/latex] later developed paralytic polio.<\/p>\n<p>Part A: A good experiment always starts with a good research question. What is the research objective or question in this experiment?<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q891968\">Hint<\/span><\/p>\n<div id=\"q891968\" class=\"hidden-answer\" style=\"display: none\">A researcher must determine the question(s) they want answered. The question(s) must clearly identify the groups to be studied. The question is usually about whether one thing causes another.<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<p>Part B: What is the factor of interest in this experiment? What is the response variable in this experiment?<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q12573\">Hint<\/span><\/p>\n<div id=\"q12573\" class=\"hidden-answer\" style=\"display: none\">Remember the factor of interest (also known as the independent variable or the explanatory variable) is the factor that the researcher purposely changes to see if it causes a specific outcome. The response variable (also known as the response factor or dependent variable) is the factor that is expected to change and will be measured at the end of the experiment.<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<p>Part C: In an experiment, subjects are often referred to as experimental units. This name emphasizes that the objects measured do not have to be human beings. They could, for example, be government buildings, department stores, animals, or computer chips. When people are the experimental units, we call them subjects, participants, or patients, depending upon the context of the study. What are the experimental units in this experiment?<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q526914\">Hint<\/span><\/p>\n<div id=\"q526914\" class=\"hidden-answer\" style=\"display: none\">Remember, the experimental units are the subjects of the experiment.<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<p>Part D: What are the treatments or levels of the factor of interest?<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q761629\">Hint<\/span><\/p>\n<div id=\"q761629\" class=\"hidden-answer\" style=\"display: none\">Remember, the treatments, also known as levels of the factor of interest, are imposed by the researcher on the groups.<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<p>An experiment will compare the recorded values of the response variable across multiple levels of the factor of interest. Often this includes the treatment of interest, but it should also have a second baseline level treatment for comparison to help with analyzing the effectiveness. The experimental units are split into two groups\u2014one group receives the treatment of interest (this is usually called the experimental group) and the other group does not. The group that does not receive the treatment of interest is the control group.<\/p>\n<p>&nbsp;<\/p>\n<p>Part E: Identify the experimental units that are in the experimental group and the experimental units that are in the control group.<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q216422\">Hint<\/span><\/p>\n<div id=\"q216422\" class=\"hidden-answer\" style=\"display: none\">Remember the experimental group consists of the experimental units that will receive the treatment of interest. The control group consists of the experimental units that will receive the placebo.<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<p>A second method of defining the control group is through the use of a placebo. The <strong>placebo effect<\/strong> is a positive response that people who believe they are receiving treatment for a condition have, even if what they are actually receiving is a placebo. It is a fascinating connection between mind and body that is still not completely understood. The placebo effect can make it difficult to gauge the effects on the response variable.<\/p>\n<p>&nbsp;<\/p>\n<p>Part F: Why is it important to use a placebo in this study?<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q830533\">Hint<\/span><\/p>\n<div id=\"q830533\" class=\"hidden-answer\" style=\"display: none\">What do <em>you<\/em> think?<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<p>In medicine, the randomized experiment (clinical trial) has become the gold standard for the evaluation of new medical treatments because of its effectiveness and ability to objectively support conclusions. The Cochrane Collaboration is an organization devoted to synthesizing evidence from medical studies all over the world. According to this organization, there have been hundreds of thousands of randomized experiments comparing medical treatments. In most countries, a company can\u2019t get a new drug approved for sale unless it has been tested in a well-designed experiment. A good experiment will randomly assign the experimental units to the treatments.<\/p>\n<p>&nbsp;<\/p>\n<p>Part G: Why is <strong>random assignment<\/strong> important?<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q102593\">Hint<\/span><\/p>\n<div id=\"q102593\" class=\"hidden-answer\" style=\"display: none\">Refer to your notes on experimental design.<\/div>\n<\/div>\n<p>In an experiment, it is important that each group be treated the same way. It is also important that the subjects do not adjust their behavior because of the treatment they are receiving. For this reason, many experiments use a technique called blinding. <strong>Blinding<\/strong> refers to nondisclosure of the treatment an experimental unit is receiving. Whoever has contact with the subjects during the experiment, including the data collectors who record the experimental units\u2019 response outcomes, should be blind to the treatment information. When neither the subject nor those having contact with the subject know the treatment assignment, the study is called <strong>double-blind<\/strong>.<\/p>\n<p>&nbsp;<\/p>\n<p><span style=\"font-size: 1rem; text-align: initial;\">Part H: Why do you think blinding is important? Would it be more ideal for a study to be a blind or double-blind study? Was blinding or double-blinding used in the experiment involving the Salk vaccine?<\/span><\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q922260\">Hint<\/span><\/p>\n<div id=\"q922260\" class=\"hidden-answer\" style=\"display: none\">What do <em>you<\/em> think?<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<p>Part I: Replication of studies increases confidence in the conclusion. Was replication achieved in the experiment involving the Salk vaccine? Explain.<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q717481\">Hint<\/span><\/p>\n<div id=\"q717481\" class=\"hidden-answer\" style=\"display: none\">Replication helps to ensure that the results of an experiment are truly caused by the change in the factor of interest and not by other hidden factors or natural variation in data. A well-designed experiment always achieves replication by including large numbers of participants. Replication can also be achieved by repeating the entire experiment with new groups of participants.<\/div>\n<\/div>\n<\/div>\n<p>Now, compile a list of the key components that you identified in Question 1. Use them to answer Question 2.<\/p>\n<div class=\"textbox key-takeaways\">\n<h3>question 2<\/h3>\n<p>In Question 1, you identified the key components that make up a well-designed experiment in Parts C, D, E, G, H, and I. Review them and use them to answer Part A below.<\/p>\n<p>&nbsp;<\/p>\n<p>Part A: List the components that should be included in a well-designed experiment.<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q557332\">Hint<\/span><\/p>\n<div id=\"q557332\" class=\"hidden-answer\" style=\"display: none\">Review your answers to Question 1 Parts C, D, E, G, H, and I.<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<p>Part B: Do you believe the experiment in Question 1 involving the Salk vaccine is an experiment that was designed well? Explain.<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q820585\">Hint<\/span><\/p>\n<div id=\"q820585\" class=\"hidden-answer\" style=\"display: none\">What do <em>you<\/em> think? Use the key components you identified to support your answer.<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<p>Part C: Would you trust any conclusions drawn from this experiment or would you be skeptical? Explain.<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q484529\">Hint<\/span><\/p>\n<div id=\"q484529\" class=\"hidden-answer\" style=\"display: none\">What do you think? Did the experiment include the key components necessary for a well-designed experiment? <\/div>\n<\/div>\n<\/div>\n<p>In Question 3, you&#8217;ll fill in the blanks to describe how many participants were assigned into each group and what was compared at the end of the experiment so that conclusions might be drawn.<\/p>\n<div class=\"textbox key-takeaways\">\n<h3>question 3<\/h3>\n<p>3) Complete the diagram below to illustrate the design of the Salk vaccine experiment.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-1124\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/5738\/2022\/01\/12010705\/Screen-Shot-2022-01-11-at-5.06.10-PM-300x100.png\" alt=\"A flowchart. The first box reads &quot;Experimental units: 401,974 subjects.&quot; It has two arrows coming out of it, both arrows are labeled &quot;randomly assigned.&quot; One of the arrows goes to a box with text reading &quot;Experimental Group&quot; and the other to another box reading &quot;Control Group.&quot; Both of these have arrows leading to another box that has nothing written in it.\" width=\"1098\" height=\"366\" \/><\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q723903\">Hint<\/span><\/p>\n<div id=\"q723903\" class=\"hidden-answer\" style=\"display: none\">How many participants were included in each group? What was compared at the end of the experiment?<\/div>\n<\/div>\n<\/div>\n<p>The Salk vaccine experiment was one of the largest health experiments ever conducted. It was an experiment because subjects were given treatments, but it&#8217;s not always possible to conduct experiments. Ethical issues, cost, time, and other considerations sometimes prohibit the use of an experiment. For example, it would be unethical to conduct an experiment on the effects of texting while driving with two treatment groups: those who text while driving and those who don&#8217;t. We would need to request half the subjects to engage in a behavior that we already suspect might cause injury or fatality. In this case, an observational study would be more appropriate, in which previously recorded vehicle collision data is observed to understand the effects of texting while driving.<\/p>\n<p>The Salk Vaccine experiment used a <strong>completely randomized design<\/strong> because the experimental units (subjects) were randomly assigned to one of two (or more) treatments. Another type of experimental design called block design, or blocking, can be added to a completely randomized design to strengthen the results. Let&#8217;s explore this type of design now.<\/p>\n","protected":false},"author":17533,"menu_order":28,"template":"","meta":{"_candela_citation":"[]","CANDELA_OUTCOMES_GUID":"","pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-316","chapter","type-chapter","status-publish","hentry"],"part":158,"_links":{"self":[{"href":"https:\/\/courses.lumenlearning.com\/alphamodule\/wp-json\/pressbooks\/v2\/chapters\/316","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/courses.lumenlearning.com\/alphamodule\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/courses.lumenlearning.com\/alphamodule\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/alphamodule\/wp-json\/wp\/v2\/users\/17533"}],"version-history":[{"count":2,"href":"https:\/\/courses.lumenlearning.com\/alphamodule\/wp-json\/pressbooks\/v2\/chapters\/316\/revisions"}],"predecessor-version":[{"id":322,"href":"https:\/\/courses.lumenlearning.com\/alphamodule\/wp-json\/pressbooks\/v2\/chapters\/316\/revisions\/322"}],"part":[{"href":"https:\/\/courses.lumenlearning.com\/alphamodule\/wp-json\/pressbooks\/v2\/parts\/158"}],"metadata":[{"href":"https:\/\/courses.lumenlearning.com\/alphamodule\/wp-json\/pressbooks\/v2\/chapters\/316\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/courses.lumenlearning.com\/alphamodule\/wp-json\/wp\/v2\/media?parent=316"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/alphamodule\/wp-json\/pressbooks\/v2\/chapter-type?post=316"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/alphamodule\/wp-json\/wp\/v2\/contributor?post=316"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/alphamodule\/wp-json\/wp\/v2\/license?post=316"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}