Psych 318-09 Section worksheet for t tests of correlations ...



Psych 318-10. Section worksheet for t tests of correlations and power of t tests

The purpose of this worksheet is to give you some practice working on null hypothesis tests for correlation coefficients (section 9.10) and on power calculations (Chapter 8).

1. A researcher is interested in determining whether a correlation exists between college grades and income 10 years after graduation. GPAs and income for a random sample of 62 graduates of Southern Washington State University were obtained. The Pearson r is computed to be .16. Is there sufficient evidence to claim that there is a positive correlation between GPA and income?

First, state the null and alternative hypotheses:

H0: (=0

H1: ((0 { (>0, ( ( OR (equivalently, but less informatively) [pic], tobt < tcrit

What can you conclude?

There is insufficient evidence to support a claim that GPA and income are positively (or negatively) correlated.

2. Another researcher is interested in determining whether the correlation between blood alcohol content and reaction time is the same for men as it is for women. The correlation for the 103 men in the study is .58 and the correlation for the 53 women in the study is .51.

First, state the null and alternative hypotheses:

H0: (f=(m

H1: (f((m, { (f>(m, (f ................
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