Statistics Normal Probabilities

The lengths of pregnancies of humans are normally distributed with a mean of 268 days and a standard

deviation of 15 days. Find the probability of a pregnancy lasting more than 300 days.

• 0.0166

• 0.9834

• 0.2375

• 0.3189

Assume that the random variable X is normally distributed, with mean μ = 80 and standard deviation σ = 15.

Compute the probability P(X > 92).

• 0.1977

• 0.2119

• 0.7881

• 0.2420

The distribution of cholesterol levels in teenage boys is approximately normal with μ = 170 and σ = 30 (Source:U.S. National Center for Health Statistics). Levels above 200 warrant attention. Find the probability that a teenage boy has a cholesterol level greater than 200.

• 0.3419

• 0.1587

• 0.8314

• 0.2138

An airline knows from experience that the distribution of the number of suitcases that get lost each week on a certain route is approximately normal with μ = 15.5 and σ = 3.6. What is the probability that during a given week the airline will lose less than 20 suitcases?

• 0.3944

• 0.1056

• 0.4040

• 0.8944

Assume that blood pressure readings are normally distributed with μ = 120 and σ = 8. A blood pressure

reading of 145 or more may require medical attention. What percent of people have a blood pressure reading

greater than 145?

• 0.09 %

• 99.91 %

• 6.06 %

• 11.09 %

Assume that the heights of American men are normally distributed with a mean of 69.0 inches and a standard

deviation of 2.8 inches. The U.S. Marine Corps requires that men have heights between 64 and 78 inches. Find

the percent of men meeting these height requirements.

• 31.12 %

• 99.93 %

• 3.67 %

• 96.26 %

The graph depicts IQ scores of adults, and those scores are normally distributed with a mean of 100 and a

standard deviation of 15. Find the probability that a member selected at random is from the shaded area of the

graph.

• 0.6293

• 0.4400

• 0.7486

• 0.8051

The graph depicts IQ scores of adults, and those scores are normally distributed with a mean of 100 and a

standard deviation of 15. Find the probability that a member selected at random is from the shaded area of the

graph.

• 0.7745

• 0.7303

• 0.7619

• 0.7938

Find the probability of z occurring in the indicated region.

• 0.2776

• 0.7224

• 0.2224

• 0.1894

Find the probability of z occurring in the indicated region.

• 0.0228

• 0.9599

• 0.0668

• 0.0401