Name: ______Period:______

Ch. 6 ReviewAP Statistics

1. A student took two national aptitude tests in the course of applying for admission to college. The national average and standard deviation for the first test were 475 and 100 respectively, whereas for the second test the average and standard deviation were 30 and 8 respectively. The student scored 625 on the first test and 45 on the second test. Determine which exam the student performed better on.

2. A zoo is looking for an unusually large jaguar for its “Big Cats” display. The body length(excluding the tail) of jaguars is known to have a mean of 1.4 meters and a standard deviation of 0.20 meters.

A. Suppose the zoo defines “unusually large” as the top 15% of jaguars in body length. What requirement would you place on their body length?

B. Redefine “unusually large” as the top 5% and repeat part A.

C. Compare your answers from parts A and B.

3. A sample of concrete specimens of a certain type is selected, and the compressive strength of each one is determined. The mean and standard deviation are calculated as 3000 and 500 respectively.

A. What percentage of sample observations are outside the interval from 2000 to 4000?

B. What percentage of sample observations are between 2500 and 3500?

C. What can be said about the approximate percentage of observations between 2000 and 2500?

4. The mean utility bill is $100 with standard deviation $12.

A. What percent of bills are more than $125?

B. What is the smallest bill that can be in the top 30% of the bills?

C. What is the highest bill that can be in the bottom 20% of the bills?

6. Some IQ tests are standardized to a Normal model, with a mean of 100 and a standard deviation of 16. Show your work (picture) when answering the following about IQ scores:

  1. (2)What interval would we expect to find 95% of the scores? ______
  1. (2)What percent of people should have IQ scores above 116? ______
  1. (2)What percent of people should have IQ scores between 68 and 84? ______
  1. (2)What would you have to score to be in the top 2.5% of IQs ______

True or False

_____8. If the standard deviation of a distribution gets larger the curve of the data will get taller.

_____9. The normal curve is always symmetric.