15. For a normal distribution, X ~ N( = 5, ²=1), what is the probability that a randomly selected observation will be greater than 5? That is, what is P(X > 5)?

17. Exact environmental concentrations of a chemical in a body of water are not quantifiable if they are too low or too high. The cutoffs for being not quantifiable are either concentrations below 100 parts per million or above 300 parts per million. Suppose we take a sample of water from which the concentration is normally distributed with mean 195 parts per million and standard deviation of 60 parts per million. What is the probability that the concentration will be at a quantifiable level?

18. Total cholesterol values in a population are normally distributed with mean 200 mg/dL and standard deviation of 30 mg/dL. Above what cholesterol level would a

a person's total cholesterol have to be for it to be above the 85^th percentile?

19. An exercise physiology study found that aerobic exercise capacity as measured by VO2max for average runners enrolled in a training class has mean 46 ml/kg/min, with a SD of 10 ml/kg/min. A group of 50 runners in the class will be used to determine if their average aerobic capacity is not too high or too low. Specifically, between 42 and 48 ml/kg/min. Find the probability that the randomly chosen group of 50 will have a sample mean in this range.