Chapter 11

Question 1

A repeated-measures design, or a within-subject design

Answer 1

A repeated-measures design, or a within-subject design, is one in which the dependent variable is measured two or more times for each individual in a single sample. The same group of subjects is used in all of the treatment conditions.

The main advantage of a repeated-measures study is that it uses exactly the same individuals in all treatment conditions. Thus, there is no risk that the participants in one treatment are substantially different from the participants in another

Question 2

matched-subjects

Answer 2

In a matched-subjects study, each individual in one sample is matched with an individual in the other sample. The matching is done so that the two individuals are equivalent (or nearly equivalent) with respect to a specific variable that the researcher would like to control.

Question 3

difference score

Answer 3

D = X2 - X1

The sample of difference scores (D values) serves as the sample data for the hypothesis test and all calculations are done using the D scores.

Question 4

related-samples

Answer 4

Two research designs that are statistically equivalent. The scores in one set are directly related, one-to-one, with the scores in the second set.

Question 5

The Hypotheses for a Related-Samples Test

Answer 5

• The researcher’s goal is to use the sample of difference scores to answer questions about the general population
• That is, we would like to know what would happen if every individual in the population were measured in two treatment conditions ( X1 and X2 ) and a difference score (D) were computed for everyone.
• We identify this population mean difference with the symbol
  μD

Question 6

the single-sample t statistic is defined by the formula

Answer 6

t = M-mu / sM

Question 7

t formula for the repeated-measures design becomes

Answer 7

t = MD-mu D / sMD

Question 8

variance (or the standard deviation) for the sample of D scores.

Answer 8

s^2 = SS/n-1 = SS/df or s = square root of SS/df

Question 9

The estimated standard error equation

Answer 9

sMD = square root of s^2/n or s/square root of n

Question 10

The related-samples t statistic requires two basic assumptions.

Answer 10

• The observations within each treatment condition must be independent
• The population distribution of difference scores (D values) must be normal.

Question 11

Cohen’s d

Answer 11

d = population mean difference/standard deviation = MD/standard deviation D

Question 12

estimated d

Answer 12

estimated d = sample mean difference/sample mean deviation = MD/s

Question 13

r^2 formula

Answer 13

r^2 = t^2/t^2+df

Question 14

the repeated-measures design has most of the advantages.

Answer 14

• A repeated-measures design typically requires fewer subjects than an independent-measures design.
• The repeated-measures design is especially well suited for studying learning, development, or other changes that take place over time.
• The primary advantage of a repeated-measures design is that it reduces or eliminates problems caused by individual differences.

Question 14

order effects

Answer 14

The effects of participating in one treatment that may influence the scores in the following treatment.

Question 15

counterbalancing

Answer 15

One way to deal with time-related factors and order effects is to counterbalance the order of presentation of treatments. That is, the participants are randomly divided into two groups, with one group receiving treatment 1 followed by treatment 2, and the other group receiving treatment 2 followed by treatment 1.