A consumer organization wants to estimate the actual tread wear index of a brand name of tires that claims “graded 200” on the sidewall of the tire. A random sample of 23 tires indicates a sample mean tread wear index of 190.7 and a sample standard deviation of 29.3.
Assuming that the population of tread wear indexes is normally distributed, construct a 90% confidence interval estimate of the population mean tread wear index for tires produced by this manufacturer under this brand name, round to two decimal places as…