Public Health and Nutrition
All across the United States, there are abandoned factories that were once used to melt lead. Soil tests in neighborhoods near some of these factory locations suggest the dirt is contaminated and that children should not play in or near the area.19 Hedley Street near the Delaware River in Philadelphia is the site of two old lead factories. Suppose samples of soil around homes in the area were obtained and the lead level in each was carefully measured (in parts per million, ppm). The data are given in the following table:
a. Construct a normal probability plot for these data. Is there any evidence to suggest non-normality?
b. Use the backward empirical rule to check for evidence of non-normality.