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- Elementary statistics: exam 3:
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.
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A
0.7981
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B
0.2019
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C
0.9999
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D
0.0001
85% of the seventh–grade students spend more than what amount per day?
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A
$2.12
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B
$0.75
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C
$4.74
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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?
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A
0.7475
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B
0.4259
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C
0.2525
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D
0.6784
60% of these students spend at most how many hours doing their homework?
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A
1.69 hours
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B
1.31 hours
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C
1.5 hours
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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.
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A
0.4441
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B
0.5559
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C
0.8944
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D
1
The middle 50% of weights of supplies carried by a randomly chosen llama is between _____ and _____.
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A
0 and 62.5 pounds
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B
58.45 and 66.55 pounds
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C
56.5 and 68.5 pounds
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D
There is not enough information given.
Which of the following are true for the normal distribution?
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I
More values fall close to the mean than fall far away from the mean.
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Ii
The mean and standard deviation cannot be the same.
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Iii
A change in µ causes the graph to shift to the left or right and changes the shape of the graph.
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Iv
A change in s causes a change in the shape of the normal curve.
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A
I, IV
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B
I, II, III, IV
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C
I, II, III
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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.
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A
.2143
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B
0.7727
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C
0.4705
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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?
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A
.2143
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B
0.7727
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C
0.4705
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D
0.375
On average, how long does a junior high school student sleep per night?
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A
9.6 hours
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B
6.5 hours
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C
7.8 hours
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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?
Source:
OpenStax, Elementarystats. OpenStax CNX. Jan 03, 2011 Download for free at http://cnx.org/content/col11263/1.1
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