Question

6. Engagement Activity: The t Test for Two Related Samples 

In the last chapter, you were introduced to Professor Ken Bonanno's Statistical Methods in Psychology class, where students are asked to complete a research study as a part of the semester-long course. Many of his students' research questions could be asked using the independent-measures t test, but there are other approaches, which will be explored in this chapter. 

Click the following topics to see some sample questions asked by Professor Bonanno's students. Select the topic that most interests you and use the research questions to answer the questions that follow. 

Compensation and Motivation Work Productivity Caffeine Intake and Academic Performance 

Research Questions

 1. Do people who drink the caffeine equivalent of at least two cups of coffee (Group A) do worse on tests than those who drink less than one cup (Group B)?

 2. Do people do better on tests when they drink the caffeine equivalent of at least two cups of coffee (Condition A) than when they drink less than one cup (Condition B)? 

Notice that both studies described are getting at the same research question (Does drinking at least two cups of coffee worsen tests results?). But, the first example studies two different populations (those people who drink the caffeine equivalent of at least two cups of coffee and those people who drink less than one cup), while the second example studies the same people twice, under two different conditions or treatments (first when people drink the caffeine equivalent of at least two cups of coffee, and then when they drink less than one cup).

Decide on a topic you would like to think more about. Once you have selected (and clicked on your topic, click Continue. Then complete the revealed exercises. 

What might be some of the advantages and disadvantages of using the repeated-measures t test compared with a research method with two separate groups (the independent-measures t test)? 

Identify which of the following are advantages of the repeated-measures t test. (Note: This is an exploratory exercise. You will be given credit regardless of your answer.) 

The repeated-measures t test can handle categorical data. 

In the repeated-measures t test the participants in one treatment are not substantially different from the participants in another. 

The repeated-measures t test can handle more than two conditions. 

The repeated-measures t test uses half the number of participants. 

In the following exercises, you will learn more about the statistical techniques that allow a researcher to use the sample data from a repeated-measures study to draw inferences about the general population.

Answer 1

Statement 1: Advantage

The repeated measures t test can handle categorical data.

Makes the experiment more efficient, validity of the results higher, and to keep the variability low.

Statement 2: Advantage

In the repeated measures t-test, the participants in one treatment are not substantially different from the participants in another, because the same subjects are used in both and through our study. This makes the researcher to get a reliable statistical conclusion even with small set of subjects.

Statement 3: Not an advantage.

The repeated measures t test can handle more than two conditions. This is a disadvantage compared to other design, where the subjects are exposed to more than one treatment.

Statement 4: Advantage.

The repeated measures t test uses half the number of participants. This method requires minimal subjects. With that we can get significant results for the given sample.