normal​ distribution

Suppose that the length of long distance phone calls, measured in minutes, is known to have an exponential distribution with the average length of a call equal to $24 minutes. The 16th percentile is a phone call that lasts minutes.

I tried the two last choice both of them are wrong.

The average American gets a haircut every 34 days. Is the average smaller for college students? The data below shows the results of a survey of 15 college students asking them how many days elapse between haircuts. Assume that the distribution of the population is normal. 35, 23, 32, 38, 31, 39, 35, 25, 30, 36, 40, 27, 23, 32, 25 What can be concluded at the the a = 0.10 level of significance level of significance? a. For this study, we should use Select an answer b. The null and alternative hypotheses would be: Ho: ?v Select an answerv Hi: ?vSelect an answerv c. The test statistic ?v = (please show your answer to 3 decimal places.) d. The p-value = (Please show your answer to 3 decimal places.) e. The p-value is 2v a f. Based on this, we should Select an answerv the null hypothesis. g. Thus, the final conclusion is that.. O The data suggest the population mean is not significantly lower than 34 at a = 0.10, so there M 24 3. 4. 5 6. 7 EU