PSYC*1010 Chapter 11: t Tests for Two Related Samples

Question 1

When is a repeated-measures t-test conducted?

Answer 1

When two sets of data from the same group are collected and compared

Question 2

In a repeated-measures test, which variable is measured two or more times for each individual in a single sample?

Answer 2

The dependent variable

Question 3

What is the main advantage to using a repeated-measures method?

Answer 3

The is no risk that participants in one treatment are substantially different from the participants in another (because the same individuals are used in all treatment conditions)

Question 4

What is the main disadvantage to using a repeated-measures method?

Answer 4

Design allows for factors other than the treatment effect to change a participant’s score (ex. time related factors)

Question 5

What is a matched-subjects design?

Answer 5

Involves two separate samples, but each individual in one sample is matched one-to-one with an individual in the other sample

Question 6

How are participants matched in a matched-subjects design?

Answer 6

Based on one or more variable considered to be especially important for the study

Question 7

The closest to perfect a match can be in a matched-subjects design is limited by what?

Answer 7

The closest to perfect a match can be is limited to the variables used for matching

Question 8

What is the common name that refers to both repeated-measures and matched-subjects designs?

Answer 8

Related-samples design

Question 9

How are difference scores typically obtained?

Answer 9

By subtracting the first score (before treatment) from the second score (after treatment)

Question 10

What does the sign of each difference score indicate?

Answer 10

The direction of change

Question 11

For a repeated-measures design, what serves as the sample data for the hypothesis test?

Answer 11

The sample of difference scores

Question 12

T or F: A selected sample from a population likely have error, so even if μD=0, MD is not expected to be exactly zero.

Answer 12

True

Question 13

In a repeated-measures t-test, what is population mean always set to?

Answer 13

Zero

Question 14

What must be calculated before computing estimated standard error in a repeated-measures test?

Answer 14

The variance/standard deviation using the sum of squares from the sample of difference scores (calculated using a table)

Question 15

What columns are included in the table used to calculate sum of squares from the sample of difference scores?

Answer 15

X1, X2, D, D^2

Question 16

What are the two basic assumptions of a repeated-measures t-test?

Answer 16

• Observations within each treatment condition must be independent
• The population distribution of difference scores must be normal (or n>30)

Question 17

What are two factors that affect confidence intervals?

Answer 17

• Percentage of confidence used
• Sample size

Question 18

How does percentage of confidence affect the size of a confidence interval?

Answer 18

Larger percentage produces a wider interval

Question 19

Why are confidence intervals not a pure, unbiased measure of effect size?

Answer 19

Because they’re influenced by sample size

Question 20

Is standard error directly or inversely related to sample size?

Answer 20

Inversely

Question 21

Is standard error directly or inversely related to sample variance?

Answer 21

Directly

Question 22

T or F: Sample size influences measures of effect size.

Answer 22

False

Question 23

T or F: Variance influences measures of effect size.

Answer 23

True

Question 24

Does a large variance produce a small or large value for the t statistic?

Answer 24

Larger variance produces a smaller value for the t statistic

Question 25

Does an independent-measures or repeated-measures design typically require fewer subjects?

Answer 25

Repeated-measures

Question 26

Does an independent-measures or repeated-measures design use participants more efficiently?

Answer 26

Repeated-measures

Question 27

Are independent-measures or repeated-measures designs more suited for studying changes that take place over time?

Answer 27

Repeated-measures

Question 28

What are individual differences?

Answer 28

Characteristics that vary from one individual to another

Question 29

What are time-related factors?

Answer 29

Factors other than the treatment effect that cause a participant’s score to change (ex. participant’s mood, weather, etc…)

Question 30

What are order effects?

Answer 30

Changes in scores that are caused by participation in an earlier treatment (ex. participant gaining experience, and thus performing better)

Question 31

What is one strategy for dealing with time-related and order effects?

Answer 31

Counterbalancing

Question 32

What does counterbalancing involve?

Answer 32

One group receives treatment 1 followed by treatment 2, and the other group receives treatment 2 followed by treatment 1

Question 33

How are degrees of freedom calculated to find the critical t value for a related-measures t-test?

Answer 33

df (sample 1) + df (sample 2)