Unit 6, Topic 24, Exercise 24-25


Many songs associate Mondays with having the blues, but are people really more likely to commit suicide on Mondays? A recent study (Kposowa et al., 2009) analyzed data on suicides in the United States between the years 2000 and 2004. They classified each suicide according to the day of the week on which it occurred. Their data produced the following sample percentages:

A news article that described this study did not report the sample size. Suppose for now that the sample size was 252. The computer output below presents results of a chi-square goodness-of-fit test of equal proportions:


a. Explain how the expected counts were calculated.


c. Interpret what the p-value means in this context.

pi Subscript Raloxifene
Upper H Subscript a Baseline colon pi Subscript Tamoxifenpi Subscript Raloxifene

The test statistic is chi Superscript 2 Baseline equals Upper H Subscript 0.

d. Suppose someone else decided to perform a two-sample z-test and found that z equals negative 0.2 and p-valueequals 0.838 Comment on how this compares to the test statistic and p-value you just calculated.

The test statistic of the chi-square test is roughly  the test statistic of the two-sample z-test.
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