Normal probability distribution

Annual salaries for a large company are approximately normally distributed with mean of RM50,000 and standard deviation of RM20,000. What percentage of company workers has a salary less than RM40,000?

• 32.03%

• 34.00%

• 30.85%

• 31.25%

The amount of time a student taking statistics spends on studying for a test is normally distributed. If the average time spent studying is 12 hours and standard deviation is 4 hours, what is the probability that a student will spent more than 8 hours studying?

• 0.8413

• 0.8013

• 0.8223

• 0.8333

Suppose that the height (X) in inches, of a 25-year-old man is a normal random variable with mean, μ= 70 inches. If P(X >79) = 0.025 what is the standard deviation of this random normal variable?

• 4.59

• 4.23

• 3.57

• 4.28

Find the z-score that has 2.68% of the distribution’s area to its right.

• z = 0.9963

• z = –1.93

• z = –0.0037

• z = 1.93

Use a correction for continuity to convert the following interval to a normal distribution interval.

The probability of getting at least 80 successes

• x > 80.5

• x > 79.5

• x < 80.5

• x < 79.5