Normal Probabilities

The average waist size for teenage males is 29 inches with a standard deviation of 1.4 inch.

If waist sizes are normally distributed, estimate the proportion of teenagers who will have waist sizes greater than 31 inches?

• 92.4%

• 10.5%

• 16%

• 7.6%

• 15.87%

• 15.39%

• 9.68%

• 84.61%

According to the empirical rule, what percentage of data falls within 1 standard deviation of the mean? 

• 25%

• 68%

• 95%

• 99.7%

Find the z-score such that the area under the standard normal curve is 0.3015

• -1.88

• 0.52

• -0.52

• 1.88

Find the z-score such that the area above the standard normal curve is 0.4404. 

• -0.15

• -1.71

• 1.71

• 0.15

Find the Z-score.

Mean = 21

Standard Deviation: 1.3

x = 22

• 0.77

• 5.33

• 1.07

• 1.26

Find the z-score.

Mean = 45

Standard Deviation: 2.1

x = 50

• 2.38

• 3.00

• 3.08

• 2.33

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

• 6

• 34

• 52

• 70

The z-table gives the percent of data at or below a z-score.

• True

• Sometimes true, sometimes false

• False

Convert the following into the original x-value using μ = 5.3 and σ = 0.4.
z = 1.51

• X = -9.475

• X = 9.475

• X = -5.904

• X = 5.904