3.Teaching Assistants' Stipends A random sample of stipends of teaching assistants in economics is listed. Is there sufficient evidence at the =0.10 level to conclude that the average stipend differs from $15,500? The stipends listed (in dollars) are for the academic year. Assume that the population is approximately normally distributed.

13,419 16,338 14,000 14,000 15,000

12,283 12,000 11,981 13,185

(a) State the hypotheses and identify the claim.

H0: = $15500 not claim

H1 : $15500 claim

This hypothesis test is a two-tailed test.

(b) Find the critical value(s). Round the answer(s) to at least three decimal places. If there is more than one critical value, separate them with commas. Critical value(s): ?

4.Cell Phone Call Lengths The average local cell phone call length was reported to be 2.17 minutes. A random sample of 21 phone calls showed an average of 2.87 minutes in length with a standard deviation of 0.94 minutes. At =0.01, can it be concluded that the average differs from the population average? Assume that the population is approximately normally distributed.

(a) State the hypotheses and identify the claim.

H0: =2.17 not claim

H1: 2.17 claim

This hypothesis test is a two-tailed test.

(b) Find the critical value(s). Round the answer(s) to at least three decimal places. If there is more than one critical value, separate them with commas. Critical value(s): ?