Hard water. 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 following display shows the relationship between Mortality and Calcium concentration for these towns:
a) Describe what you see in this scatterplot, in context.
b) Here is the regression analysis of Mortality and Calcium concentration. What is the regression equation?
c) Interpret the slope and y-intercept of the line, in context.
d) The largest residual, with a value of -348.6, is for the town of Exeter. Explain what this value means.
e) The hardness of Derby s municipal water is about 100 ppm of calcium. Use this equation to predict the mortality rate in Derby.
f) Explain the meaning of R-squared in this situation.