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# Exam 3: Chapters 5, 6, & 7

Summary: Practice final exam for use with Collaborative Statistics (col10522) by Barbara Illowsky and Susan Dean.

• A. 0.7981
• B. 0.2019
• C. 0.9999
• D. 0.0001

A

## Exercise 3

85% of the seventh–grade students spend more than what amount per day?

• A. $2.12 • B.$0.75
• C. $4.74 • D.$0.41

D

## Questions 4 – 5 refer to the following:

The amount of time that intermediate algebra students at Leland High School spend doing their homework per day is normally distributed with a mean 1.5 hours and standard deviation 0.75 hours.

## Exercise 4

If one student is randomly chosen, what is the probability that the student does intermediate algebra homework at least 2 hours per day?

• A. 0.7475
• B. 0.4259
• C. 0.2525
• D. 0.6784

C

## Exercise 5

60% of these students spend at most how many hours doing their homework?

• A. 1.69 hours
• B. 1.31 hours
• C. 1.5 hours
• D. 0.2533 hours

A

## Questions 6 – 7 refer to the following:

Llamas are excellent pack animals. It is known that the weight of supplies carried by llamas follows a normal distribution with a mean of 62.5 pounds and a standard deviation of 6 pounds.

## Exercise 6

Find the probability that the weight of supplies carried by one randomly chosen llama is between 60 and 70 pounds.

• A. 0.4441
• B. 0.5559
• C. 0.8944
• D. 1

B

## Exercise 7

The middle 50% of weights of supplies carried by a randomly chosen llama is between _____ and _____.

• A. 0 and 62.5 pounds
• B. 58.45 and 66.55 pounds
• C. 56.5 and 68.5 pounds
• D. There is not enough information given.

B

## Exercise 8

Which of the following are true for the normal distribution?

• I. More values fall close to the mean than fall far away from the mean.
• II. The mean and standard deviation cannot be the same.
• III. A change in µ causes the graph to shift to the left or right and changes the shape of the graph.
• IV. A change in s causes a change in the shape of the normal curve.
• A. I, IV
• B. I, II, III, IV
• C. I, II, III
• D. III, IV

A

## Questions 9 – 13 refer to the following:

The length of time junior high school students sleep per night follows an approximate uniform distribution from seven to eleven hours. Suppose we randomly select a junior high student.

## Exercise 9

Find the probability that the randomly selected student sleeps less than 8 1/2 hours per night.

• A. .2143
• B. 0.7727
• C. 0.4705
• D. 0.375

D

## Exercise 10

Find the probability that the randomly selected student sleeps eight to twelve hours per night.

• A. 0
• B. 1
• C. 0.75
• D. 0.25

C

## Exercise 11

On average, how long does a junior high school student sleep per night?

• A. .2143
• B. 0.7727
• C. 0.4705
• D. 0.375

B

## Exercise 12

On average, how long does a junior high school student sleep per night?

• A. 9.6 hours
• B. 6.5 hours
• C. 7.8 hours
• D. 8.4 hours

D

## Exercise 13

We are interested in the probability that a randomly selected student sleeps less than eight hours, knowing that he/she sleeps less than ten. Which graph best depicts this situation?

• A.
• B.
• C.
• D.

C

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