Statistic

10. The length of useful life of a fluorescent tube used for indoor gardening is normally distributed. The useful life has mean of 600 hours and standard deviation of 40 hr. Determine the probability that a. such a tube will last less than 730 hr. b. Find the 44" percentile. 11. The U.S. National Center for Health Statistics reports that 60% of those with artificial hip and knee joints are female; If 30 of these people are selected at random, find the probability that fewer than 15 are female. 12. The Oak Grove College financial aid office did a study showing that their students spend an average (mean) of $680 in the college bookstore on books and supplies per year. The standard deviation is $138. If a random sample of 36 students is surveyed. What is the probability that the mean amount spent for books and supplies is less than $600