1. A tire manufacturer wants to estimate the average number of miles that may be driven on attire of a certain type before the tire wears out. A random sample of 32 tires is chosen; the tires are driven on until they wear out, and the number of miles driven on each tire is recorded. The data, in thousands of miles, are as follows:
32, 33, 28,37, 29, 30, 25, 27, 39, 40, 26, 26, 27, 30, 25, 30, 31, 29, 24, 36, 25, 37, 37, 20, 22, 35, 23, 28, 30, 36, 40, 41
Give a 99% confidence interval for the average number of miles that may be driven on a tire of this kind.
2. A stock market analyst wants to estimate the average return on a certain stock. A random sample of 15 days yields an average (annualized) return of x- = 10.37% and a standard deviation s = 3.5%. Assuming a normal population of returns, give a 95% confidence interval for the average return on this stock.
3. List three different sampling methods and explain their differences.
4. Discuss three problems that may arise in the process of designing or conducting a focus group. In particular, to what extent can moderators anticipate the likely directions (and misdirection's) the discussion may take?