In an investigation of environmental causes of disease, data were collected on the annual mortality rate (deaths per 100,000) for males in 61 large towns in England and Wales. In addition, the water hardness was recorded as the calcium concentration (parts per million, ppm) in the drinking water. The data set also notes for each town whether it was south or north of Derby. Is there a significant difference in mortality rates in the two regions? Here are the summary statistics.

Summary of: mortality

For categories in: Derby

Group Count Mean Median StdDev

North 34 1631.59 1631 138.470

South 27 1388.85 1369 151.114

USE MINITAB:

a)Test appropriate hypotheses and state your

conclusion.

b)The boxplots of the two distributions show an

outlier among the data north of Derby. What effect

might that have had on your test?

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