Question

Group #1: Smashed into mean and SD: Mean = 42.45, Variance = 45.31, SD = 6.73

Group #2: Hit mean and SD:   M = 31.30, Variance = 38.43, SD = 6.20

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 =2.10

B. Cohen’s d =1.12

C. Cohen’s d =2.50

D. Cohen’s d =2.13

2. What does the pooled Cohen’s d you obtained using the "how fast" study data represent?

A. No effect

B. A small/weak effect

C. A large effect

D. A medium/moderate effect

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

Answer 1

A -

Cohen's d is calculated according to the formula: d = (M₁ – M₂ ) / SD_pooled

SD_pooled = √[ (SD₁² + SD₂²) / 2 ]

Where:

M₁ = group 1 mean,

M₂ = group 2 mean,

SD₁ = group 1 standard deviation,

SD₂ = group 2 standard deviation

SD_pooled = standard deviation (pooled).

M₁ = 42.45, M₂ = 31.3, SD₁ = 6.73, SD₂ = 6.2

d = (42.45 – 31.3) / 6.47, SD_pooled = √[ (6.73² + 6.2²) / 2 ] = 6.47

d = 11.150 / 6.47 = 1.723

d = 1.723

The cohen's effect size suggests a large effect

Effect size means the gap between the mean values of two groups in relation to standard deviation.

Effect size helps in comprehending the difference between two groups.

The Cohen's d statistic is calculated by determining the difference between two mean values and dividing it by the population standard deviation