




Practice final exam for use with Collaborative Statistics (col10522) by Barbara Illowsky and Susan Dean.
Questions 1 – 3 refer to the following:
Assume the amount of money seventh–grade students spend on food each day at school is exponentially distributed with an average of $2.50.
Which graph best describes the distribution?
Find the probability that a randomly selected seventh–grade student spends less than $4 a day on food.

A
0.7981

B
0.2019

C
0.9999

D
0.0001
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
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.
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
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
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.
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
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.
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
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.
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
Find the probability that the randomly selected student sleeps eight to twelve hours per night.
On average, how long does a junior high school student sleep per night?

A
.2143

B
0.7727

C
0.4705

D
0.375
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
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?
Questions & Answers
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Source:
OpenStax, Collaborative statistics for mt230: supplemental course materials. OpenStax CNX. Jan 12, 2012 Download for free at http://legacy.cnx.org/content/col11351/1.2
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