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).

Section 1Section 2Sample Size100100Mean34.436.2Standard Deviation5.85.9(a)

Calculate the test statistic and itsp-value to test for a difference in the two population means. (UseSection 1Section 2.Round your test statistic to two decimal places and yourp-value to four decimal places.)

z=p-value=

Use thep-value to evaluate the statistical significance of the results at the 5% level.

H₀is not rejected. There is sufficient evidence to indicate a difference in the mean lead levels for the two sections of the city.

H₀is rejected. There is insufficient evidence to indicate a difference in the mean lead levels for the two sections of the city.

H₀is not rejected. There is insufficient evidence to indicate a difference in the mean lead levels for the two sections of the city.

H₀is rejected. There is sufficient evidence to indicate a difference in the mean lead levels for the two sections of the city.

(b)

Calculate a 95% confidence interval to estimate the difference in the mean lead levels in parts per million for the two sections of the city. (UseSection 1Section 2.Round your answers to two decimal places.)

parts per million toparts per million

(c)

Suppose that the city environmental engineers will be concerned only if they detect a difference of more than5 partsper million in the two sections of the city. Based on your confidence interval in part (b), is the statistical significance in part (a) ofpractical significanceto the city engineers? Explain.

Since all of the probable values of₁₂given by the interval are all greater than 5, it is likely that the difference will be more than 5 ppm, and hence the statistical significance of the difference is of practical importance to the the engineers.

Since all of the probable values of₁₂given by the interval are all less than5, it is likely that the difference will be more than 5 ppm, and hence the statistical significance of the difference is of practical importance to the the engineers.

Since all of the probable values of₁₂given by the interval are between5 and 5, it is not likely that the difference will be more than 5 ppm, and hence the statistical significance of the difference is not of practical importance to the the engineers.