Chapter 9 - Within-Subjects Design

Question 1

What is a within-subjects design?

Answer 1

When an experiment uses a single group of participants and tests or observes each individual in all of the different treatments being compared

Question 2

What is the structure of a within-subject design?

Answer 2

1. One sample of participants ➔ the participants are measured in the first treatment ➔ the same participants are measured in the second treatment ➔ the same participants are measured in the third treatment
2. One sample of participants ➔ all treatments administered together

Question 3

What is another word for a within subject design?

Answer 3

Repeated-measures design

Question 4

What are 2 advantages of within-subjects design?

Answer 4

1. Requires less participants
2. Eliminates the problem of individual differences

Question 5

What are 2 disadvantages of within-subjects design?

Answer 5

1. Potential for time-related factors
   - participants go through treatment conditions at different times
   - can provide alternative explanations for the results
2. Participant attrition
   - some participants may drop out of the study before it is completed
   - usually when the experiment is too long

Question 6

What are 2 sources of confounding variables?

Answer 6

1. Confounding from environmental variables
2. Confounding from time-related variables

Question 7

What is order effects?

Answer 7

Order effects is when a change, that IS NOT from the treatment, occurs from one treatment condition to the another

Question 8

How many participants would be needed for a within-subjects experiment comparing four different treatment conditions with a total of 20 scores in each treatment?

Answer 8

20

Question 9

In a within-subjects research study comparing different treatment conditions at different times, what kind of validity is threatened by factors that change over time, such as history and maturation?

Answer 9

Internal Validity

Question 10

What is counterbalancing?

Answer 10

Counterbalancing is the process of matching treatments with respect to time

Question 11

What is the goal for counterbalancing?

Answer 11

To eliminate time-related confounding

Question 12

What is complete counterbalancing?

Answer 12

A series of treatments is presented in every possible sequence.

Question 13

To use complete counter balancing on four treatment conditions, how many different sequences are there?

Answer 13

There are 24 different sequences.
4! = 4 x 3 x 2 x 1 = 24

Question 14

What is the effect of increasing the time between treatment conditions in a within-subjects experiment?

Answer 14

It decreases the threat of the order effect fatigue.

Question 15

For a within-subjects study comparing two treatments, A and B, a researcher expects that practice in the first treatment will improve the participants’ scores in the second treatment. If the order of treatments is counterbalanced, then what scores will be influenced by the practice?

Answer 15

Scores in treatment A for half the participants and scores in treatment B for half the participants

Question 16

What is an advantage of the between-subjects design versus the within-subjects design?

Answer 16

It eliminates the risk of order effects.

Question 17

For an experiment that compares two treatment conditions with ten scores in each treatment, which design would require fewer subjects?

Answer 17

Within-subjects design