Chapter PI, Problem 15RE

(a)

To determine

To find out what were the variables in this study and indicate whether it is quantitative or categorical and what are the units are.

Answer to Problem 15RE

The variables are annual mortality rate and water hardness.

Explanation of Solution

It is given in the question that an investigation was carried out on the environmental causes of disease on the annual mortality rates. Thus, annual mortality rate for males is one of the variable and it is quantitative as it is numeric in nature and its units is given in deaths per $100,000$ and the other variable is water hardness which is also quantitative and its units is in parts per million.

(b)

To determine

To describe the distributions of the two variables.

Explanation of Solution

It is given in the question that an investigation was carried out on the environmental causes of disease on the annual mortality rates. Thus, as we can see from the histograms that calcium is skewed to the right, possibly bimodal. There looks to be a mode down near $12$ ppm that is the center of a fairly tight symmetric distribution and another mode near $62.5$ ppm that is the center of much more spread out symmetric almost uniform distribution. Mortality however, appears uni-modal and symmetric with the mode near $1500$ deaths per $100,000$ .