Homework # 7 Name ______________________________

Chapters 11 & 13

1. Under what conditions would we use a correlated groups t-test? (½ pt)

 

 

2. When do we refer to a research design as being "within-subjects"? (½ pt)

 

 

3. What is the rationale behind counter-balancing the sequence of conditions across participants in a within-subjects design? (¾ pt)

 

 

4. How does the interpretation of eta² in the context of a correlated groups t-test differ from its interpretation in the context of an independent groups t-test? (1 pt)

 

 

 

5. Define and distinguish the SS_total, SS_IV, SS_error, and SS_{across subjects}. (1 pt)

 

 

 

 

 

4b. How are the interrelated? (¼ pt)

 

6. We are interested in studying the effects of distraction on reading. The following table presents the number of pages participants were able to read in 5 minutes under three levels of distraction (low, moderate and high). Use this data to calculate intermediate values for SS components (2 pts), create a summary table (2 pts), and report your critical value and decision (½ pt). Then analyze the strength (1 pt) and the nature of the relationship (1 pt). Be sure to show all work for necessary calculations!

Student	Low	Moderate	High
1	5	7	2
2	9	7	5
3	8	5	6
4	6	5	4
5	9	6	6

7. A video game company releases special booklet full of helpful hints for easier and faster methods of conquering the various levels a popular video game. We conduct a study to investigate whether the tips provided in the book allow players to conquer the first level more quickly than they would without the tips. In a within-subjects design, participants in our sample first play the game before learning of the helpful hints. Then the participants play the video game again after learning the tips for how to beat the first level faster. The time (in minutes) it takes each person to conquer the first level is measured both before and after learning the helpful hints. Use a correlated groups t-test to determine whether learning the tips helps people to conquer the first level of the game faster.

Participant	Before Hints	After Hints	D	D2
1	2.3	1.4
2	2.7	2.0
3	3.5	2.7
4	2.9	2.0
5	4.0	3.4
6	3.5	2.8
7	1.8	1.6
8	2.9	2.5
9	3.9	3.3
10	3.4	3.4
11	2.9	2.3
12	2.9	1.8

a) What are your degrees of freedom (df) and critical t value? (½ pt)

b) Complete above table (1 pt)

3. Compute the SS_D: (½ pt)

 

4. Compute the estimated standard error of the mean of difference scores: (1 pt)

c) Compute the t: (½ pt)

d) What is your decision regarding H_O? (¼ pt)

e) How strong is the relationship between the IV and DV? (½ pt)

f) Describe the nature of the relationship: (¼ pt)