Statistics: Principles and Methods, 7th Edition

2

Organization and Description of Data

1 Main Types of Data

2 Describing Data by Tables and Graphs

3 Measures of Center

4 Measures of Variation

5 Checking the Stability of the Observations Over Time

6 More on Graphics

Acid Rain Is Killing Our Lakes

Acid precipitation is linked to the disappearance of sport fish and other organisms from lakes. Sources of air pollution, including automobile emissions and the burning of fossil fuels, add to the natural acidity of precipitation.

The Wisconsin Department of Natural Resources initiated a precipitation monitoring program with the goal of developing appropriate air pollution controls to reduce the problem. The acidity of the first 50 rains monitored, measured on a pH scale from 1 (very acidic) to 7 (basic), are summarized by the histogram.

Notice that all the rains are more acidic than normal rain, which has a pH of 5.6. (As a comparison, apples are about pH 3 and milk is about pH 6.)

Researchers in Canada have established that lake water with a pH below 5.6 may severely affect the reproduction of game fish. More research will undoubtedly improve our understanding of the acid rain problem and lead, it is hoped, to an improved environment.

In Chapter 1, we cited several examples of situations where the collection of data by experimentation ...