{"id":3546,"date":"2022-03-02T15:59:36","date_gmt":"2022-03-02T15:59:36","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/lumen-danacenter-statsmockup\/?post_type=chapter&#038;p=3546"},"modified":"2022-04-12T15:15:21","modified_gmt":"2022-04-12T15:15:21","slug":"what-to-know-about-2e","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/lumen-danacenter-statsmockup\/chapter\/what-to-know-about-2e\/","title":{"raw":"Forming Connections in 2E: Advanced Experimental Design","rendered":"Forming Connections in 2E: Advanced Experimental Design"},"content":{"raw":"<div class=\"textbox learning-objectives\">\r\n<h3>Objectives for this activity<\/h3>\r\nDuring this activity, you will:\r\n<ul>\r\n \t<li style=\"font-weight: 400;\" aria-level=\"1\">Describe the role that blocking plays in an experiment.<\/li>\r\n \t<li style=\"font-weight: 400;\" aria-level=\"1\">Identify the basic principles of the completely randomized block design.<\/li>\r\n \t<li style=\"font-weight: 400;\" aria-level=\"1\">Describe how to use a completely randomized block design for a given research objective.<\/li>\r\n<\/ul>\r\n<\/div>\r\nYou've seen experiments and observational studies and compared their advantages and disadvantages in use as tools for research. In the preview\u00a0<em>What to Know\u00a0<\/em>page for this activity, you learned what completely randomized design and blocking are in experiments. In this activity, you'll add to your understanding of the key components necessary for a well-designed experiment by learning how to design an experiment using the completely randomized block design. Along the way, you'll understand the purpose of blocking and see that a well-designed experiment helps to determine whether the appropriate conclusion is made.\r\n<h2>\u00a0Advanced Experimental Design<\/h2>\r\nIn the last few activities, you have been exploring key components of well-designed experiments. Another key component of well-designed experiments is randomization.\r\n\r\n*image*\r\n\r\nLet\u2019s revisit the polio experiment from Preview Assignment 2.E. Recall that in the 1950s, a large-scale experiment was designed to test the effectiveness of the Salk vaccine in preventing polio. Children were assigned to either the experimental or the control group through random assignment. Suppose that the experimental group of 200,745 children received Salk vaccine injections, while a control group of 201,229 children were injected with a placebo. None of the children knew whether or not they had received the vaccine or the placebo. Among the children given the Salk vaccine, 33 later developed paralytic polio, but among the children given a placebo, 115 later developed paralytic polio.\r\n\r\nThink individually about the role that randomization played in this experiment, then share your thoughts with a partner and answer Question 1.\r\n<div class=\"textbox key-takeaways\">\r\n<h3>question 1<\/h3>\r\nWhat role did randomization play in this experiment?\r\n\r\n[reveal-answer q=\"574755\"]Hint[\/reveal-answer]\r\n[hidden-answer a=\"574755\"]Consider what randomly assigning participants helps to ensure.[\/hidden-answer]\r\n\r\n<\/div>\r\n<div class=\"textbox tryit\">\r\n<h3>Guidance<\/h3>\r\n<span style=\"background-color: #e6daf7;\">[Intro: The basic principles of the completely randomized block design are blocking and randomization.\u00a0 Randomization allows the researcher to create comparable groups--that is, groups that have similar distributions of the other factors. In other words, the researcher is trying to ensure that the factors in one group are similar to the factors in the other group. Imagine that the health conditions of a subject in this experiment could play a role in how subjects respond to a treatment (in this case, the Salk vaccine injection or the placebo injection). Random assignment helps to ensure that one group won't be much \"healthier\" than the other group. In this activity, you'll explore the role that blocking plays in an experiment and use it to describe how completely randomized block design can be used for a given research objective.\u00a0 ]<\/span>\r\n\r\n<\/div>\r\nWork together to complete the diagram in Question 2. Some questions to ask as you do so include:\r\n<ul>\r\n \t<li>How do we determine which experimental units form the blocks?<\/li>\r\n \t<li>What is the purpose of blocking?<\/li>\r\n \t<li>How are the experimental units assigned to the experimental treatments?<\/li>\r\n \t<li>Is the purpose of a completely randomized block design to determine whether differences between blocks result in any differences in the value of the response factor?<\/li>\r\n<\/ul>\r\n<div class=\"textbox key-takeaways\">\r\n<h3>Question 2<\/h3>\r\nAnother way a researcher might conduct an experiment is by using a <strong>completely randomized block design<\/strong>. This design is used when the experimental units are divided into homogeneous groups called blocks. Within each block, the experimental units are randomly assigned to treatments. Complete the following diagram to illustrate this design.\r\n\r\n<img class=\"alignnone wp-image-1126\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/5738\/2022\/01\/12010715\/Screen-Shot-2022-01-11-at-5.03.38-PM-300x200.png\" alt=\"A flowchart. On the far left is &quot;Experimental Units,&quot; which has two arrows leading from it to boxes labeled &quot;Block 1&quot; and &quot;Block 2,&quot; respectively. &quot;Block 1&quot; has an arrow leading to a box labeled &quot;Experimental Group&quot; and another to a box labeled &quot;Control Group.&quot; &quot;Experimental Group&quot; and &quot;Control Group&quot; each have an arrow leading from them to the same blank box. From &quot;Block 2,&quot; there is an arrow leading to a different box labeled &quot;Experimental Group&quot; and another box labeled &quot;Treatment 2&quot; Both of these boxes have an arrow leading to a different blank box. The two blank boxes have a two-way arrow between them.\" width=\"792\" height=\"528\" \/>\r\n\r\n[reveal-answer q=\"670777\"]Hint[\/reveal-answer]\r\n[hidden-answer a=\"670777\"]Experimental units are placed in homogenous (similar) blocks, and are then randomly assigned to treatments. Which group receives the treatment of interest and which gets the placebo? At the end of the experiment, what is compared? [\/hidden-answer]\r\n\r\n<\/div>\r\n<div class=\"textbox tryit\">\r\n<h3>Guidance<\/h3>\r\n<span style=\"background-color: #e6daf7;\">[Sub-summary: How did you do with Question 2? It can be difficult sometimes to understand what the question is asking you to do. Just keep in mind that the idea behind completely randomized block design is that blocking holds nuisance factors constant while the factor of interest is allowed to vary. For example, if it is known that the hearts of men and women respond differently to medicine, an experiment that tests the effectiveness of aspirin on heart disease might create a block of men and a block of women to hold the factor of gender constant across the treatment and placebo groups. The key to using completely randomized block design is to first create the blocks, then randomly assign participants within each block to the treatment groups. ]<\/span>\r\n\r\n<\/div>\r\nWork in small groups to answer Questions 3 - 6.\r\n<div class=\"textbox key-takeaways\">\r\n<h3>question 3<\/h3>\r\nA school psychologist wants to test the effectiveness of a new method for teaching reading. She recruits 80 first-grade students in District Code 75104 and randomly divides them into two groups. Group 1 is taught by means of the new method, while Group 2 is taught by the traditional method. The same teacher is assigned to teach both groups. At the end of the year, an achievement test is administered and the results are compared.\r\n\r\n&nbsp;\r\n\r\nPart A: What is the factor of interest? What is the response variable?\r\n\r\n[reveal-answer q=\"151292\"]Hint[\/reveal-answer]\r\n[hidden-answer a=\"151292\"]What do <em>you<\/em> think? What is it that gets manipulated and what is compared at the end?[\/hidden-answer]\r\n\r\n&nbsp;\r\n\r\nPart B: What are some factors, other than the factor of interest, in the study that could affect test scores? How are they controlled?\r\n\r\n[reveal-answer q=\"250468\"]Hint[\/reveal-answer]\r\n[hidden-answer a=\"250468\"]What other factors are given in the scenario? Are the students limited to a particular grade level or a single teacher, for example? [\/hidden-answer]\r\n\r\n&nbsp;\r\n\r\nPart C: What are the treatment groups?\r\n\r\n[reveal-answer q=\"336699\"]Hint[\/reveal-answer]\r\n[hidden-answer a=\"336699\"]Include the treatment of interest as well as the control.[\/hidden-answer]\r\n\r\n&nbsp;\r\n\r\nPart D: What are the experimental units (or subjects)?\r\n\r\n[reveal-answer q=\"151841\"]Hint[\/reveal-answer]\r\n[hidden-answer a=\"151841\"]In this case, who is receiving the treatments?[\/hidden-answer]\r\n\r\n&nbsp;\r\n\r\nPart E: Are there any factors that cannot be controlled that might affect the test results? How can we minimize the effect that this variable may have on the outcome?\r\n\r\n[reveal-answer q=\"686487\"]Hint[\/reveal-answer]\r\n[hidden-answer a=\"686487\"]What do <em>you<\/em> think?[\/hidden-answer]\r\n\r\n&nbsp;\r\n\r\nPart F: Previous research indicates that girls and boys may react differently to the two methods of instruction (there are an even number of girls and boys).\u00a0 How can you design an experiment that will control the effects due to gender on the scores on the achievement test (the response factor)? Complete the following template to illustrate your design.<img class=\"alignnone wp-image-1126\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/5738\/2022\/01\/12010715\/Screen-Shot-2022-01-11-at-5.03.38-PM-300x200.png\" alt=\"A flowchart. On the far left is &quot;Experimental Units,&quot; which has two arrows leading from it to boxes labeled &quot;Block 1&quot; and &quot;Block 2,&quot; respectively. &quot;Block 1&quot; has an arrow leading to a box labeled &quot;Experimental Group&quot; and another to a box labeled &quot;Control Group.&quot; &quot;Experimental Group&quot; and &quot;Control Group&quot; each have an arrow leading from them to the same blank box. From &quot;Block 2,&quot; there is an arrow leading to a different box labeled &quot;Experimental Group&quot; and another box labeled &quot;Treatment 2&quot; Both of these boxes have an arrow leading to a different blank box. The two blank boxes have a two-way arrow between them.\" width=\"792\" height=\"528\" \/>\r\n\r\n[reveal-answer q=\"263107\"]Hint[\/reveal-answer]\r\n[hidden-answer a=\"263107\"]Remember, blocks are made of homogenous groups whose members are then randomly assigned to treatments. At the end, the response variable (achievement test results in this case) are compared within each block and across blocks. [\/hidden-answer]\r\n\r\n<\/div>\r\n<div class=\"textbox tryit\">\r\n<h3>Guidance<\/h3>\r\n<span style=\"background-color: #e6daf7;\">[Sub-summary: How are you doing so far? Are you starting to develop a mental landscape for completely randomized block design? If so, try answering these questions in your notes:<\/span>\r\n<ul>\r\n \t<li>First, recall the key components of good experimental design.\r\n[reveal-answer q=\"607207\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"607207\"]Factor of interest, response factor, nuisance factors, treatments, and random assignment.[\/hidden-answer]<\/li>\r\n \t<li><span style=\"background-color: #e6daf7;\">What are the basic principles of the completely randomized block design?<\/span>\r\n[reveal-answer q=\"934614\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"934614\"]Blocking and randomization[\/hidden-answer]<\/li>\r\n \t<li><span style=\"background-color: #e6daf7;\">What role does each principle play in the design?<\/span>\r\n[reveal-answer q=\"450675\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"450675\"]Blocking aids in minimizing the effects of nuisance factors. Randomization is used to assign subjects within the blocks to the treatment groups to help ensure that the groups have similar distributions of factors other than the factor of interest.[\/hidden-answer]<\/li>\r\n<\/ul>\r\n<\/div>\r\nContinue to use this scenario first given in Question 3 to answer Questions 4 - 6.\r\n\r\n<em>A school psychologist wants to test the effectiveness of a new method for teaching reading. She recruits 80 first-grade students in District Code 75104 and randomly divides them into two groups. Group 1 is taught by means of the new method, while Group 2 is taught by the traditional method. The same teacher is assigned to teach both groups. At the end of the year, an achievement test is administered and the results are compared.<\/em>\r\n<div class=\"textbox key-takeaways\">\r\n<h3>question 4<\/h3>\r\nWhat are some advantages of using the completely randomized block design for the education researcher in the scenario given in Question 3?\r\n\r\n[reveal-answer q=\"92890\"]Hint[\/reveal-answer]\r\n[hidden-answer a=\"92890\"]Consider the advantages of blocking and of random assignment.[\/hidden-answer]\r\n\r\n<\/div>\r\n<div class=\"textbox key-takeaways\">\r\n<h3>question 5<\/h3>\r\nAgain, referring to the scenario given in Question 3, would you consider this experiment to be well-designed?\r\n\r\n[reveal-answer q=\"40348\"]Hint[\/reveal-answer]\r\n[hidden-answer a=\"40348\"]Does it include the key features of experimental design?[\/hidden-answer]\r\n\r\n<\/div>\r\n<div class=\"textbox key-takeaways\">\r\n<h3>question 6<\/h3>\r\nWould you trust the results from the conclusions of this experiment or would you be skeptical?\r\n\r\n[reveal-answer q=\"229406\"]Hint[\/reveal-answer]\r\n[hidden-answer a=\"229406\"]We can trust the results of a well-designed experiment.[\/hidden-answer]\r\n\r\n<\/div>\r\n<div class=\"textbox tryit\">\r\n<h3>Guidance<\/h3>\r\n<span style=\"background-color: #e6daf7;\">[Wrap-up: The key components of a well-designed experiment include treatment, factor of interest (also known as the explanatory variable or independent variable), response variable (also known as the dependent variable), nuisance factors, random assignment, and replication. <\/span>\r\n\r\n<span style=\"background-color: #e6daf7;\">The completely randomized block design is an additional method we can use to control for a known difference that affects the response factor. <\/span>\r\n\r\n<span style=\"background-color: #e6daf7;\">The basic principles of a completely randomized block design are blocking and randomization.<\/span>\r\n\r\n<span style=\"background-color: #e6daf7;\">Blocking helps to minimize the effects of nuisance factors. Randomization is used to assign subjects within the blocks to the treatment groups,\u00a0which helps ensure that the groups have similar distributions of factors other than the factor of interest.<\/span>\r\n\r\n<span style=\"background-color: #e6daf7;\">We can trust the conclusions of a well-designed experiment. The results of a well-designed and implemented study are meaningful. ]<\/span>\r\n\r\n<\/div>\r\n&nbsp;","rendered":"<div class=\"textbox learning-objectives\">\n<h3>Objectives for this activity<\/h3>\n<p>During this activity, you will:<\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\">Describe the role that blocking plays in an experiment.<\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\">Identify the basic principles of the completely randomized block design.<\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\">Describe how to use a completely randomized block design for a given research objective.<\/li>\n<\/ul>\n<\/div>\n<p>You&#8217;ve seen experiments and observational studies and compared their advantages and disadvantages in use as tools for research. In the preview\u00a0<em>What to Know\u00a0<\/em>page for this activity, you learned what completely randomized design and blocking are in experiments. In this activity, you&#8217;ll add to your understanding of the key components necessary for a well-designed experiment by learning how to design an experiment using the completely randomized block design. Along the way, you&#8217;ll understand the purpose of blocking and see that a well-designed experiment helps to determine whether the appropriate conclusion is made.<\/p>\n<h2>\u00a0Advanced Experimental Design<\/h2>\n<p>In the last few activities, you have been exploring key components of well-designed experiments. Another key component of well-designed experiments is randomization.<\/p>\n<p>*image*<\/p>\n<p>Let\u2019s revisit the polio experiment from Preview Assignment 2.E. Recall that in the 1950s, a large-scale experiment was designed to test the effectiveness of the Salk vaccine in preventing polio. Children were assigned to either the experimental or the control group through random assignment. Suppose that the experimental group of 200,745 children received Salk vaccine injections, while a control group of 201,229 children were injected with a placebo. None of the children knew whether or not they had received the vaccine or the placebo. Among the children given the Salk vaccine, 33 later developed paralytic polio, but among the children given a placebo, 115 later developed paralytic polio.<\/p>\n<p>Think individually about the role that randomization played in this experiment, then share your thoughts with a partner and answer Question 1.<\/p>\n<div class=\"textbox key-takeaways\">\n<h3>question 1<\/h3>\n<p>What role did randomization play in this experiment?<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q574755\">Hint<\/span><\/p>\n<div id=\"q574755\" class=\"hidden-answer\" style=\"display: none\">Consider what randomly assigning participants helps to ensure.<\/div>\n<\/div>\n<\/div>\n<div class=\"textbox tryit\">\n<h3>Guidance<\/h3>\n<p><span style=\"background-color: #e6daf7;\">[Intro: The basic principles of the completely randomized block design are blocking and randomization.\u00a0 Randomization allows the researcher to create comparable groups&#8211;that is, groups that have similar distributions of the other factors. In other words, the researcher is trying to ensure that the factors in one group are similar to the factors in the other group. Imagine that the health conditions of a subject in this experiment could play a role in how subjects respond to a treatment (in this case, the Salk vaccine injection or the placebo injection). Random assignment helps to ensure that one group won&#8217;t be much &#8220;healthier&#8221; than the other group. In this activity, you&#8217;ll explore the role that blocking plays in an experiment and use it to describe how completely randomized block design can be used for a given research objective.\u00a0 ]<\/span><\/p>\n<\/div>\n<p>Work together to complete the diagram in Question 2. Some questions to ask as you do so include:<\/p>\n<ul>\n<li>How do we determine which experimental units form the blocks?<\/li>\n<li>What is the purpose of blocking?<\/li>\n<li>How are the experimental units assigned to the experimental treatments?<\/li>\n<li>Is the purpose of a completely randomized block design to determine whether differences between blocks result in any differences in the value of the response factor?<\/li>\n<\/ul>\n<div class=\"textbox key-takeaways\">\n<h3>Question 2<\/h3>\n<p>Another way a researcher might conduct an experiment is by using a <strong>completely randomized block design<\/strong>. This design is used when the experimental units are divided into homogeneous groups called blocks. Within each block, the experimental units are randomly assigned to treatments. Complete the following diagram to illustrate this design.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-1126\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/5738\/2022\/01\/12010715\/Screen-Shot-2022-01-11-at-5.03.38-PM-300x200.png\" alt=\"A flowchart. On the far left is &quot;Experimental Units,&quot; which has two arrows leading from it to boxes labeled &quot;Block 1&quot; and &quot;Block 2,&quot; respectively. &quot;Block 1&quot; has an arrow leading to a box labeled &quot;Experimental Group&quot; and another to a box labeled &quot;Control Group.&quot; &quot;Experimental Group&quot; and &quot;Control Group&quot; each have an arrow leading from them to the same blank box. From &quot;Block 2,&quot; there is an arrow leading to a different box labeled &quot;Experimental Group&quot; and another box labeled &quot;Treatment 2&quot; Both of these boxes have an arrow leading to a different blank box. The two blank boxes have a two-way arrow between them.\" width=\"792\" height=\"528\" \/><\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q670777\">Hint<\/span><\/p>\n<div id=\"q670777\" class=\"hidden-answer\" style=\"display: none\">Experimental units are placed in homogenous (similar) blocks, and are then randomly assigned to treatments. Which group receives the treatment of interest and which gets the placebo? At the end of the experiment, what is compared? <\/div>\n<\/div>\n<\/div>\n<div class=\"textbox tryit\">\n<h3>Guidance<\/h3>\n<p><span style=\"background-color: #e6daf7;\">[Sub-summary: How did you do with Question 2? It can be difficult sometimes to understand what the question is asking you to do. Just keep in mind that the idea behind completely randomized block design is that blocking holds nuisance factors constant while the factor of interest is allowed to vary. For example, if it is known that the hearts of men and women respond differently to medicine, an experiment that tests the effectiveness of aspirin on heart disease might create a block of men and a block of women to hold the factor of gender constant across the treatment and placebo groups. The key to using completely randomized block design is to first create the blocks, then randomly assign participants within each block to the treatment groups. ]<\/span><\/p>\n<\/div>\n<p>Work in small groups to answer Questions 3 &#8211; 6.<\/p>\n<div class=\"textbox key-takeaways\">\n<h3>question 3<\/h3>\n<p>A school psychologist wants to test the effectiveness of a new method for teaching reading. She recruits 80 first-grade students in District Code 75104 and randomly divides them into two groups. Group 1 is taught by means of the new method, while Group 2 is taught by the traditional method. The same teacher is assigned to teach both groups. At the end of the year, an achievement test is administered and the results are compared.<\/p>\n<p>&nbsp;<\/p>\n<p>Part A: What is the factor of interest? What is the response variable?<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q151292\">Hint<\/span><\/p>\n<div id=\"q151292\" class=\"hidden-answer\" style=\"display: none\">What do <em>you<\/em> think? What is it that gets manipulated and what is compared at the end?<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<p>Part B: What are some factors, other than the factor of interest, in the study that could affect test scores? How are they controlled?<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q250468\">Hint<\/span><\/p>\n<div id=\"q250468\" class=\"hidden-answer\" style=\"display: none\">What other factors are given in the scenario? Are the students limited to a particular grade level or a single teacher, for example? <\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<p>Part C: What are the treatment groups?<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q336699\">Hint<\/span><\/p>\n<div id=\"q336699\" class=\"hidden-answer\" style=\"display: none\">Include the treatment of interest as well as the control.<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<p>Part D: What are the experimental units (or subjects)?<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q151841\">Hint<\/span><\/p>\n<div id=\"q151841\" class=\"hidden-answer\" style=\"display: none\">In this case, who is receiving the treatments?<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<p>Part E: Are there any factors that cannot be controlled that might affect the test results? How can we minimize the effect that this variable may have on the outcome?<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q686487\">Hint<\/span><\/p>\n<div id=\"q686487\" class=\"hidden-answer\" style=\"display: none\">What do <em>you<\/em> think?<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<p>Part F: Previous research indicates that girls and boys may react differently to the two methods of instruction (there are an even number of girls and boys).\u00a0 How can you design an experiment that will control the effects due to gender on the scores on the achievement test (the response factor)? Complete the following template to illustrate your design.<img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-1126\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/5738\/2022\/01\/12010715\/Screen-Shot-2022-01-11-at-5.03.38-PM-300x200.png\" alt=\"A flowchart. On the far left is &quot;Experimental Units,&quot; which has two arrows leading from it to boxes labeled &quot;Block 1&quot; and &quot;Block 2,&quot; respectively. &quot;Block 1&quot; has an arrow leading to a box labeled &quot;Experimental Group&quot; and another to a box labeled &quot;Control Group.&quot; &quot;Experimental Group&quot; and &quot;Control Group&quot; each have an arrow leading from them to the same blank box. From &quot;Block 2,&quot; there is an arrow leading to a different box labeled &quot;Experimental Group&quot; and another box labeled &quot;Treatment 2&quot; Both of these boxes have an arrow leading to a different blank box. The two blank boxes have a two-way arrow between them.\" width=\"792\" height=\"528\" \/><\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q263107\">Hint<\/span><\/p>\n<div id=\"q263107\" class=\"hidden-answer\" style=\"display: none\">Remember, blocks are made of homogenous groups whose members are then randomly assigned to treatments. At the end, the response variable (achievement test results in this case) are compared within each block and across blocks. <\/div>\n<\/div>\n<\/div>\n<div class=\"textbox tryit\">\n<h3>Guidance<\/h3>\n<p><span style=\"background-color: #e6daf7;\">[Sub-summary: How are you doing so far? Are you starting to develop a mental landscape for completely randomized block design? If so, try answering these questions in your notes:<\/span><\/p>\n<ul>\n<li>First, recall the key components of good experimental design.\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q607207\">Show Answer<\/span><\/p>\n<div id=\"q607207\" class=\"hidden-answer\" style=\"display: none\">Factor of interest, response factor, nuisance factors, treatments, and random assignment.<\/div>\n<\/div>\n<\/li>\n<li><span style=\"background-color: #e6daf7;\">What are the basic principles of the completely randomized block design?<\/span>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q934614\">Show Answer<\/span><\/p>\n<div id=\"q934614\" class=\"hidden-answer\" style=\"display: none\">Blocking and randomization<\/div>\n<\/div>\n<\/li>\n<li><span style=\"background-color: #e6daf7;\">What role does each principle play in the design?<\/span>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q450675\">Show Answer<\/span><\/p>\n<div id=\"q450675\" class=\"hidden-answer\" style=\"display: none\">Blocking aids in minimizing the effects of nuisance factors. Randomization is used to assign subjects within the blocks to the treatment groups to help ensure that the groups have similar distributions of factors other than the factor of interest.<\/div>\n<\/div>\n<\/li>\n<\/ul>\n<\/div>\n<p>Continue to use this scenario first given in Question 3 to answer Questions 4 &#8211; 6.<\/p>\n<p><em>A school psychologist wants to test the effectiveness of a new method for teaching reading. She recruits 80 first-grade students in District Code 75104 and randomly divides them into two groups. Group 1 is taught by means of the new method, while Group 2 is taught by the traditional method. The same teacher is assigned to teach both groups. At the end of the year, an achievement test is administered and the results are compared.<\/em><\/p>\n<div class=\"textbox key-takeaways\">\n<h3>question 4<\/h3>\n<p>What are some advantages of using the completely randomized block design for the education researcher in the scenario given in Question 3?<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q92890\">Hint<\/span><\/p>\n<div id=\"q92890\" class=\"hidden-answer\" style=\"display: none\">Consider the advantages of blocking and of random assignment.<\/div>\n<\/div>\n<\/div>\n<div class=\"textbox key-takeaways\">\n<h3>question 5<\/h3>\n<p>Again, referring to the scenario given in Question 3, would you consider this experiment to be well-designed?<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q40348\">Hint<\/span><\/p>\n<div id=\"q40348\" class=\"hidden-answer\" style=\"display: none\">Does it include the key features of experimental design?<\/div>\n<\/div>\n<\/div>\n<div class=\"textbox key-takeaways\">\n<h3>question 6<\/h3>\n<p>Would you trust the results from the conclusions of this experiment or would you be skeptical?<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q229406\">Hint<\/span><\/p>\n<div id=\"q229406\" class=\"hidden-answer\" style=\"display: none\">We can trust the results of a well-designed experiment.<\/div>\n<\/div>\n<\/div>\n<div class=\"textbox tryit\">\n<h3>Guidance<\/h3>\n<p><span style=\"background-color: #e6daf7;\">[Wrap-up: The key components of a well-designed experiment include treatment, factor of interest (also known as the explanatory variable or independent variable), response variable (also known as the dependent variable), nuisance factors, random assignment, and replication. <\/span><\/p>\n<p><span style=\"background-color: #e6daf7;\">The completely randomized block design is an additional method we can use to control for a known difference that affects the response factor. <\/span><\/p>\n<p><span style=\"background-color: #e6daf7;\">The basic principles of a completely randomized block design are blocking and randomization.<\/span><\/p>\n<p><span style=\"background-color: #e6daf7;\">Blocking helps to minimize the effects of nuisance factors. Randomization is used to assign subjects within the blocks to the treatment groups,\u00a0which helps ensure that the groups have similar distributions of factors other than the factor of interest.<\/span><\/p>\n<p><span style=\"background-color: #e6daf7;\">We can trust the conclusions of a well-designed experiment. The results of a well-designed and implemented study are meaningful. ]<\/span><\/p>\n<\/div>\n<p>&nbsp;<\/p>\n","protected":false},"author":493460,"menu_order":63,"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-3546","chapter","type-chapter","status-publish","hentry"],"part":3418,"_links":{"self":[{"href":"https:\/\/courses.lumenlearning.com\/lumen-danacenter-statsmockup\/wp-json\/pressbooks\/v2\/chapters\/3546","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/courses.lumenlearning.com\/lumen-danacenter-statsmockup\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/courses.lumenlearning.com\/lumen-danacenter-statsmockup\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/lumen-danacenter-statsmockup\/wp-json\/wp\/v2\/users\/493460"}],"version-history":[{"count":16,"href":"https:\/\/courses.lumenlearning.com\/lumen-danacenter-statsmockup\/wp-json\/pressbooks\/v2\/chapters\/3546\/revisions"}],"predecessor-version":[{"id":4480,"href":"https:\/\/courses.lumenlearning.com\/lumen-danacenter-statsmockup\/wp-json\/pressbooks\/v2\/chapters\/3546\/revisions\/4480"}],"part":[{"href":"https:\/\/courses.lumenlearning.com\/lumen-danacenter-statsmockup\/wp-json\/pressbooks\/v2\/parts\/3418"}],"metadata":[{"href":"https:\/\/courses.lumenlearning.com\/lumen-danacenter-statsmockup\/wp-json\/pressbooks\/v2\/chapters\/3546\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/courses.lumenlearning.com\/lumen-danacenter-statsmockup\/wp-json\/wp\/v2\/media?parent=3546"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/lumen-danacenter-statsmockup\/wp-json\/pressbooks\/v2\/chapter-type?post=3546"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/lumen-danacenter-statsmockup\/wp-json\/wp\/v2\/contributor?post=3546"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/lumen-danacenter-statsmockup\/wp-json\/wp\/v2\/license?post=3546"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}