Chapter 11-Study Guide Exam 3

Question 1

When is a repeated measures design used?

Answer 1

• When the standard deviation is unknown, you cannot estimate the population mean, and you are examing only one sample

Ex. the stroop effect (have each particpant complete both conditions)

-there is no cotrol group, data consist of two scores for each individual- use difference scores to determine the effect of the conditions

Question 2

What is the difference between an independent-measures design and a repeated measures design? When would you use which?

Answer 2

• An independent measures is for examining two samples, repeated measures is for testing a hypothesis about the population mean difference between two measurements using a single sample

Question 3

What are the strengths of using a repeated-measures design over an independent measures design?

Answer 3

• Repeated-measures designs require fewer participants than needed for an independent-measures design because individual differences in performance from one participant to another are eliminated (reduces the variance between subjects=reduces the estimated standard error=increased power)
• Repeated-measures designs are also well suited for examining changes that occur over time (like learning or development)

Question 4

What are the weaknesses of using a repeated-measures design over an independent measures design?

Answer 4

• Testing effects: exposure to the first condition may influence scores in the second condition (e.g. practice on an IQ test in the first condition may cause improved performance in the second condition)
• Floor and Ceiling effects: occur when an individual’s score is so low in condition 1 that they have nowhere to go but up in condition 2 (floor effects) and occur when an individual has such a high score in condition 1 there is nowhere to go but down in condition 2 (ceiling effects)

Question 5

Null hypothesis and alternative hypothesis for non-directional (two-tailed) repeated-measures test

Answer 5

• Null- H0: μD = 0
• Alternative- H1: μD ≠ 0

Question 6

Null hypothesis and alternative hypothesis for directional (one-tailed) repeated-measures test

Answer 6

Null- HO: μD ≤ 0
Alternative- H1: μD > 0

Question 7

How to calculate a repeated-measures t-statistic?

Answer 7

• (MD - μD) / SMD
• df= n-1

D= X2 - X1

But uD is 0, so practically speaking numerator= Md

Question 8

Cohen’s d for repeated measures

Answer 8

Md-uD / SD