Basic Computation: Testing m1  m2 Two populations have mound-shaped, symmetrical distributions. A random sample of 16 measurements from the fi rst population had a sample mean of 20, with sample standard deviation 2.

An independent random sample of 9 measurements from the second population had a sample mean of 19, with sample standard deviation 3.

Test the claim that the population mean of the fi rst population exceeds that of the second. Use a 5% level of signifi cance.

(a) Check Requirements What distribution does the sample test statistic follow?

Explain.

(b) State the hypotheses.

(c) Compute x1  x2 and the corresponding sample test statistic.

(d) Estimate the P-value of the sample test statistic.

(e) Conclude the test.

(f) Interpret the results.

(g) Find a 90% confi dence interval for m1  m2. Explain the meaning of the confi dence interval in the context of the problem.