Question

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): Major Section 1 Section2 32 38.1 5.7 5.8 Find a 95% confidence interval for lower limit upper limit- 1712 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, should these city engineers be concerned? Explain ° At the 5% significance level, there is sufficient evidence of a difference between μ1 and μ2. The evidence suggests that μι differs from μ2 by more than 5 parts per million, so the city engineers should be concerned At the 5% significance level, there is sufficient evidence of a difference between μ1 and μ2. The evidence suggests that μ1 does not differ from μ2 by more than 5 parts per million, so the city engineers should not be concerned At the 5% significance level, there is not sufficient evidence of a difference between μ1 and μ2, so the city engineers should not be concerned None of the above

Answer 1

The statistical software output for this problem is:

Two sample Z summary confidence interval: : Mean of population 1 (Std. dev. 5.7) μ2 : Mean of population 2 (Std. dev: 5.8) -H2:Difference between two means 95% confidence interval results: Difference n1 n2 Sample mean Std. err. L.mit U. limit μι-μ2 100 100 6.1 0.81320354-7.69 38497-4.5061503

Hence,

Lower limit = -7.6938

Upper limit = -4.5062

Option C is correct.