Normal Probability Z Table

A line up for tickets to a local concert had an average (mean) waiting time of 20 minutes with a standard deviation of 4 minutes. If 2000 ticket buyers were in line, how many of them would expect to wait for less than 16 minutes?

• 1750

• 30

• 320

• 100

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. What percent of teenage boys have cholesterol levels greater than 225?

• 46.64 %

• 3.36 %

• 6.06 %

• 56.13 %

Use the image of the normal graph provided. What is the value of the mean?

• 6

• 34

• 52

• 70

A university's entrance exam scores are normally distributed with a mean of 70 and a standard deviation of 10. What is the probability that a randomly selected student scores more than 85?

• 0.0668

• 0.1587

• 0.0228

• 0.8413

A bank's loan processing time is normally distributed with a mean of 15 days and a standard deviation of 4 days. What is the probability that a randomly selected loan is processed in less than 12 days?

• 0.2266

• 0.1587

• 0.8413

• 0.9772

The average score on a math test is 75 with a standard deviation of 8. What is the probability that a randomly selected student scores between 70 and 80?

• 0.3085

• 0.2417

• 0.4680

• 0.3829

The average number of hours of sleep a person gets is 7 hours with a standard deviation of 3 hour. What is the probability that a randomly selected person sleeps more than 8.5 hours?

• 0.1587

• 0.3085

• 0.1915

• 0.0668

TRUE or FALSE: The standard normal distribution of a random variable is a normal distribution with mean =0 and standard deviation =1.

• TRUE

• FALSE

TRUE or FALSE: The area that corresponds to z = 2.58 is the same as the area that corresponds to z = -2.58, which is A = 0.4951

• TRUE

• FALSE

Find the area that corresponds to z = -1.15