1

Select one answer.

10 points

Suppose the scores on an exam are normally distributed with a mean = 75 points, and standard deviation = 8 points.

The instructor wanted to "pass" anyone who scored above 69. What proportion of exams will have passing scores?

Click here to download the normal table

1. 0.1587
2. 0.75
3. 0.2266
4. 0.7734
5. 0.75

Question 2

Select one answer.

10 points

Suppose the time to complete a 200-meter backstroke swim for female competitive swimmers is normally distributed with a mean = 141 seconds and a standard deviation = 7 seconds.

What is the completion time for the 200-meter backstroke for a female with a z-score of 1.64? (Round answer to 1 decimal place.)

1. 129.5
2. 130.8
3. 141.0
4. 152.5

Question 3

Type numbers in the boxes.

10 points

Suppose the scores on an exam are normally distributed with a mean = 75 points, and standard deviation = 8 points.

Suppose that the top 4% of the exams will be given an A+. In order to be given an A+, an exam must earn at least what score? Report your answer in whole numbers.

Question 4

Select one answer.

10 points

The following histogram displays the distribution of battery life (in hours) for a certain battery model used in cell phones:

Suppose that battery life is a normal random variable with = 8 and = 1.2. Using the standard deviation rule, what is the probability that a randomly chosen battery will last between 6.8 and 9.2 hours?

1. 0.50
2. 0.68
3. 0.95
4. 0.997

Question 5

Select one answer.

10 points

The number of days (X) after mailout it takes a utility company to receive payment for a customers bill is a normal random variable with a mean of 31 days and a standard deviation of 6 days.

The latest 2.5% of bills will be receivedmore thanhow many days after mailout?

1. 13
2. 19
3. 25
4. 31
5. 37
6. 43
7. 49

Question 6

Type numbers in the boxes.

10 points

According to the Bureau of Labor Statistics, in May 2014 the mean hourly wage of a social worker was $28.08 with a standard deviation of $1.97. Jeronica is a social worker with an hourly wage of $31.60. What is Jeronicas z-score? (Round your answer to 2 decimal places.)

Question 7

Select one answer.

10 points

The lifetime in miles for a certain brand of tire is normally distributed with a mean of 22,000 miles and a standard deviation of 3,100 miles The tire manufacturer wants to offer a money-back guarantee so that no more than 3% of tires will qualify for a refund. What is the minimum number of miles the manufacturer should guarantee that the tires will last?

1. 25,007 miles
2. 27,828 miles
3. 16,172 miles
4. 15,800 miles