Intro to Standard Deviation

In a factory, the weight of the concrete poured into a mold by a machine follows a normal distribution with a mean of 1150 pounds and a standard deviation of 22 pounds. Approximately 99.7% of molds filled by this machine will hold weights in what interval? 

• 1084 to 1216 pounds 

• 1106 to 1150 pounds 

• 1106 to 1194 pounds 

• 1128 to 1172 pounds

Which interval shows 95% of the data given a mean of 15 and a standard deviation of 3? 

• 9 to 21

• 12 to 18

• 6 to 24

• 13 to 16

The shelf life of a particular dairy product is normally distributed with a mean of 12 days and a standard deviation of 3 days.

About what percent of the products last between 12 and 15 days?

• 68%

• 34%

• 16%

• 2.5%

A distribution is normally distributed. What percent of the data falls OUTSIDE three standard deviations of the mean?

• 99.7%

• 5%

• 3%

• 0.3%

What percent of the data falls BELOW the mean?

• 50%

• 49.85%

• 68%

• 33%

Joanne's score on a test gives her a Z-score is -1.50. What does this mean?

• Joanne didn't take the test yet.

• Joanne's test score is 1.50 standard deviations below the average test score.

• Joanne did better than 1.50 times her peers.

• Joanne's test score, on average, was 1.5 points lower than the other test scores.

Find the z-score.

Mean = 40

Standard Deviation: 1.4

x = 42

• 1.43

• 1.28

• -1.4

• 1.24

What is the Z-score for Tina if she got a 31 on the ACT, the mean was 23 and the SD was 4?

• +0.20

• +2.00

• -2.00

• -0.20

Given a mean of 75 and a standard deviation of 7, what percentage of scores are between 54 and 96?

• 34%

• 99.7%

• 95%

• 2.5%

Given a mean of 75 and a standard deviation of 7, what percentage of scores are above 82?

• 34%

• 81.5%

• 16%

• 2.5%