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SAME STUDY: Jon wants to know if people who live alone have more pets than peopl

ID: 3320409 • Letter: S

Question

SAME STUDY: Jon wants to know if people who live alone have more pets than people who live with others. To test this hypothesis, Jon collects data from a random sample of n = 122 Americans. He finds that 61 people in his sample live alone and have a mean number of pets of M = 1.5 with a standard deviation of s = 0.5. He finds that n = 61 people in his sample live with others and have a mean number of pets of M = 1 with a standard deviation of s = 1.

Jon wants to conduct an independent samples t-test to see if results suggest that people who live alone have significantly ( = .01) more pets than people who live with others.

Jon computes a t-observed (Step 3) for his sample of 2.890. What does the effect size (r2) tells you about the differences/variance in number of pets.

6.5% of all the differences in one’s living situation is due to number of pets

Explanation / Answer

For the independent samples T-test, Cohen's d is determined by calculating the mean difference between your two groups, and then dividing the result by the pooled standard deviation.

Cohen's d = (M2 - M1) SDpooled

where:

SDpooled = ((SD12 + SD22) 2)

Cohen's d = (1 - 1.5) 0.790569 = 0.632456.

So,

Effect size emphasises the size of the difference rather than confounding this with sample size.

6.5% of all the differences in number of pets is due to one’s living situation