Question

Group #1: Smashed into mean and SD: Mean = 41.55, Variance = 44.15, SD = 6.64

Group #2: Hit mean and SD:   M = 27.6, Variance = 53.94, SD = 7.34

1). Compute the effect size (Cohen’s d using the pooled variance). Which of the following is the effect size? Round 2 decimal points.

A. Cohen’s d =2.13

B. Cohen’s d =1.12

C. Cohen’s d =1.99

D.Cohen’s d =2.10

2). What does the pooled Cohen’s d you obtained using the coin study data represent?

A. A small/weak effect

B. No effect

C. A large effect

D. A medium/moderate effect

3). What is the effect size and why do we report it?

EXPLAIN

4). When is it appropriate to use a dependent samples t-Test?

A. Participants are of different gender

B. Participants are randomly assigned to a group

C. Participants are recruited after completing a screening questionnaire

D. Participants provide more than one score or they are matched

5). Results Section write up: Cognitive ability of participants before and after participants consumed alcohol was recorded. Results showed a significant difference in cognitive ability before and after alcohol consumption, t(28) = 4.89, p < .01. Participants had higher scores on the cognitive task before they consumed alcohol (M = 4.55, SD = 1.11) than after (M = 2.22, SD = .09).

Using the write up of the results section from an APA empirical research article, identify which test was conducted?

A. z-test

B. Pearson correlation

C. Independent sample t-test

D. Dependent sample t-test

6). Results Section write up: Differences between treatment and control groups were tested. Results showed a significant difference between groups, t(38) = 3.45, p < .01. Participants in the treatment condition, who received study materials, had significantly higher GRE scores (M = 4.55, SD = 1.11) than participants in the control condition, who did not receive study materials (M = 2.22, SD = .09).

Using the write up of the results section from an APA empirical research article, identify which test was conducted?

A. Pearson correlation

B. z-test

C. Dependent sample t-test

D. Independent sample t-test

Answer 1

1)

Answer: C. Cohen’s d =1.99

Explanation:

The cohen's d value is obtained using the following formula,

where,

since the sample size is not given, let n1=n2=2

Now,

2)

Answer: C. A large effect

Explanation:

The Cohen's d > 0.8 considers as a large effect.

3)

The effect sized gives the standardized distance between the distribution mean. This effect size help us to determine whether this difference is important such that if the difference is 0.2 standard deviation or less we say that there is a small effect which means there is no difference between the two distribution.

4)

Answer: Participants provide more than one score or they are matched

Explanation:

When the repeated measures are done on same subject and the scores are mathced, the dependent samples t-Test is used to test the hypothesis.

5)

Answer: D. Dependent sample t-test

Explanation:

Since we are taking the repeated measures on the participant's (such that before and after the alcohol consumed), cognitive ability, the Dependent sample t-test is used.

6)

Answer: D. Independent sample t-test

Explanation:

Since we are comparing the mean GRE score of two independent groups (treatment and control), the independent sample t-test is used.