Learning Goals
In this support activity you’ll become familiar with the following:
- Distinguish between explanatory and response variables.
- Calculate and interpret changes in the response variable.
- Given a research scenario, create a table to record data on explanatory/response variables.
- Identify explanatory and response variables in a scenario.
- Determine whether there are restrictions on what kind of variables can be explanatory and response variables.
You will also have an opportunity to refresh the following skills:
- Identify whether a variable is categorical or quantitative.
In the next preview assignment and in the next class, you will need to identify and work with explanatory and response variables in experiments. Prepare for that in this corequisite support activity by assessing your own comfort level with methods for measuring and recording categorical and quantitative variables. As you work through this activity, you’ll become familiar with new terminology that will appear in the upcoming course section.
Measuring and Recording Variables
You may remember from previous activities that there are many different types of variables in statistics. In addition to understanding the differences between the types of variables, it is important to know how to measure and record each type of variable. This will help you plan data collection for your own research, as well as read and understand other researchers’ work.
You may work with a partner to complete Questions 1 – 3. As you do, make note of new vocabulary. You may wish to refresh the definitions of categorical and quantitative in the recall box below.
Recall
Core skill:
Now you try it by answering Question 1.
Question 1
1) A class is exploring the effect of physical activity on heart rate. Students measure their heart rates before and after engaging in physical activities of their choice. The heart rates in beats per minute (bpm) for five of the students are listed in the following table.
| Student ID | Heart Rate Before Activity
(in bpm) |
Heart Rate
After Activity (in bpm) |
| 01 | 82 | 74 |
| 02 | 76 | 84 |
| 03 | 64 | 78 |
| 04 | 80 | 92 |
| 05 | 72 | 84 |
Part A: The explanatory variable, also referred to as the independent variable or factor of interest, is the variable that is of interest to the researcher and is controlled by the researcher. In this research study, physical activity is the explanatory variable. The researcher is interested in the effects of physical activity. Is activity a categorical or quantitative variable?
Part B: The response variable, also referred to as the dependent variable, allows the researcher to objectively compare the differences in the levels of the factor of interest. In this study, the response variable is the students’ heart rates. Measuring heart rates allows the researchers to compare the effect of the activity—before versus after. Is heart rate a categorical or quantitative variable?
Part C: The class wants to calculate the differences between the two heart rates to complete the analysis. Complete the table below using positive numbers for scores that increased and negative numbers for scores that decreased.
| Student ID | Heart Rate Before Activity
(in bpm) |
Heart Rate
After Activity (in bpm) |
Change in Heart Rate
(in bpm) |
| 01 | 82 | 74 | |
| 02 | 76 | 84 | |
| 03 | 64 | 78 | |
| 04 | 80 | 92 | |
| 05 | 72 | 84 |
Part D: What do you notice about the change in heart rates? What effect do you think the physical activity had? Explain.
Part E: The class decides to refine their research by testing the impact of different kinds of physical activity over a period of 10 minutes. One group will practice yoga poses, another will walk at a moderate pace, and a third will run up and down the stairs as many times as possible. Create a table that the class can use to record the data then describe what will be recorded in the rows and columns of your table to answer this question.
Did you note the new vocabulary that appeared in Question 1? Here is a summary of the new terms. Be sure to list these in your notes to prepare for the upcoming course section.
- Explanatory Variable: (also, independent variable or factor of interest), the variable that is of interest to the researcher and is controlled by the researcher. This is what is suspected to cause a change in the response variable. In the above scenario, this was the physical activity, which was suspected to cause an increase in heart rate.
- Response Variable: (also, dependent variable), allows the researcher to objectively compare the differences in the levels of the factor of interest. This is what is suspected to be affected by the explanatory variable. In the above scenario, this was heartrate, which was suspected to be effected by physical activity.
Now let’s look at a different scenario and try to identify the explanatory and response variables.
Question 2
2) A psychologist is studying the effect of age on mental health by sending out online questionnaires that collect birth dates and depression scores on a scale from 1 (not at all depressed) to 4 (severely depressed).
Part A: What is the explanatory variable in this study? What type of variable is it, categorical or quantitative?
Part B: What is the response variable in this study? What type of variable is it?
Part C: The researcher downloads the data from the questionnaires and receives the following table. What does the researcher need to do to the data to be able to answer the original research question?
| Participant ID | Date of Birth | Depression Score |
| 01 | 12/13/1957 | 4 |
| 02 | 04/05/1958 | 1 |
| 03 | 07/08/1934 | 2 |
| 04 | 08/25/1994 | 1 |
| 05 | 03/15/2001 | 3 |
Now, let’s look back and consider the types of variables present in the two different scenarios above.
question 3
3) Look back at the two examples. Do you think there are restrictions on what kinds of variables can be explanatory and response variables in research? Explain.
You’ve learned quite a bit about explanatory and response variables in this support activity! Hopefully you feel comfortable enough with the terminology to move on to the What to Know page and Forming Connections activity to learn about experiments and experimental design.
