15. 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 information on lead levels (in parts per million):

a. Calculate the test statistic and its p-value to test for a difference in the two population means. Use the p-value to evaluate the significance of the results at the 5% level.

b. Use a 95% confidence interval to estimate the difference 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