Assume the time spent (in days) waiting for a heart transplant for people ages 35-49 can be approximated by a normal distribution with mean of 203 days and a standard deviation of 25.7 days. What waiting time represents the 5th percentile? What waiting time represents the third quartile?

Assume the average time spent sleeping ( in hours) for a group of medical residents at a hospital can be approximated by a normal distribution with a mean of 6.1 hours and a standard deviation of 1.0 hours. What is the shortest time spent sleeping that would still place a resident in the top 5% of sleeping times? Between what two values does the middle 50% of the sleep time lie?

Assume that a population's IQ is normally distributed with a mean of 100 and a standard deviation of 15. Would it be unusual for the mean IQ of a sample of 35 to be 115 or more? The solution to this question requires the use and understanding of the Central Limit Theorem (CLT).  While we can use the rule-of-thumb that a sample whose standard deviation is greater than 2 standard deviations is an unusual event I suggest that a preferred measure to use is a probability of less than or equal to 0.05.