Page 2 . Suppose that a population's distribution is graphed below. For each distribution, would a sampling distribution of sample means be approximately normal if the samples are of size 15? How about 100? a) b) 12 13 14 15 16 17 18 19 9 10 11 12 13 14 15 3. The mean and standard deviation of a normally distributed population are, respectively, 115 and 27. Suppose that a sample of size 9 is taken from this population. Determine the mean and standard deviation of the sampling distribution of the sample mean x . 4. The average amount of time that people spend going through airport security at a busy airport is 21 minutes. Assume that the time spent is normally distributed and the population standard deviation is 4.2 minutes a) Calculate the probability that a randomly chosen person spends more than a half an hour going through airport security. Page 1 of 6 RVCC Statistics I b) Of 40 randomly selected people, Calculate the probability that their mean time in airport security is less than 19 minutes. 5. The lifetime of a certain brand of light bulb is normally distributed with a mean of 250 hours. Assume that the population standard deviation is 50 hours. a) Calculate the probability that the lifetime of a light bulb is between 235 and 260 hours. b) Given a random sample of 60 bulbs selected, Calculate the probability that the average lifetime of the 60 bulbs is between 235 and 260 hours. ViewSonic