9.24 Lead Levels in Drinking Water Analyses of drinking water samples for 100 homes in each of two different sections of a city gave the following means and standard deviations of lead levels (in parts per million):  a. Calculate the test statistic and its p-value (observed significance level) to test for a difference in the two population means. Use the p-value to evaluate the statistical significance of the results at the 5% level.

b. Use a 95% confidence interval to estimate the dif- ference in the mean lead levels for the two sections of the city.

c. Suppose that the city environmental engineers will be concerned only if they detect a difference of more than 5 parts per million in the two sections of the city. Based on your confidence interval in part

b, is the statistical significance in part a of practical significance to the city engineers? Explain.

Transcribed Image Text:

Section 1 Section 2 Sample size 100 100 Mean 34.1 36.0 Standard deviation 5.9 6.0