Question

Biologists studying the healing of skin wounds measured the rate at which new cells closed a cut made in the skin of an anesthetized newt. Here are data from a random sample of 18 newts, measured in micrometers (millionths of a meter) per hour:

29, 27, 34, 40, 22, 28, 14, 35, 26, 35, 12, 30, 23, 18, 11, 22, 23, 33

(b) Regardless of your answer to (a), assume the population distribution is normal and use that assumption to create a 90% CI for µ, the population mean rate. (Use a calculator to find ¯x and s and then use the formula provided in class to prepare for exams. Then check your answer with R if you wish.)

(c) Consider a test of H0 : µ = 25 vs. HA : µ 6= 25 using significance level 0.10 (not the usual 0.05). Based on your 90% interval and no new calculations, say whether you would reject H0.

(d) Test whether these data are strong evidence that the population mean rate is significantly greater than 25 at level α = .05. (Note that you found a 90% confidence interval, not a 95% interval, and the interval was two-sided, but this test is one-sided, so the interval isn’t directly useful for deciding this test.)

I only really need help with C and D.

Answer 1