Let x be a random variable that represents the level ofglucose in the blood (milligrams per deciliter of blood) after a 12hour fast. Assume that for people under 50 years old, xhas a distribution that is approximately normal, with mean? = 72 and estimated standard deviation ? = 41. Atest result x < 40 is an indication of severe excessinsulin, and medication is usually prescribed.

(a) What is the probability that, on a single test, x< 40? (Round your answer to four decimal places.)


(b) Suppose a doctor uses the average x for two teststaken about a week apart. What can we say about the probabilitydistribution of x? Hint: See Theorem 6.1.

The probability distribution of x is not normal.Theprobability distribution of x is approximately normal with?_x = 72 and?_x = 20.50.    Theprobability distribution of x is approximately normal with?_x = 72 and?_x = 28.99.The probabilitydistribution of x is approximately normal with?_x = 72 and?_x = 41.

What is the probability that x < 40? (Round your answerto four decimal places.)


(c) Repeat part (b) for n = 3 tests taken a week apart.(Round your answer to four decimal places.)


(d) Repeat part (b) for n = 5 tests taken a week apart.(Round your answer to four decimal places.)


(e) Compare your answers to parts (a), (b), (c), and (d). Did theprobabilities decrease as n increased?

YesNo