Question 1

Given the following frequency distribution for test scores, what is the class midpoint for the interval 40-59?

Scores: 40-59, 60-79, 80-99
Number of students: 2, 4, 6

$$	ext{Class midpoint} = \frac{	ext{Lower limit} + 	ext{Upper limit}}{2}$$

Accepted Answer

$$49.5$$

Question 2

A frequency distribution summarizes employee years of service for Alpha Corporation. The classes are 1-5, 6-10, 11-15, 16-20, 21-25. What is the width of each class?

$$	ext{Class width} = 	ext{Upper limit} - 	ext{Lower limit} + 1$$

Accepted Answer

$$5$$

Question 3

The frequency distribution below summarizes home sale prices in the city of Summerville for June. What is the class midpoint for the class 225.0-269.9?

$$	ext{Class midpoint} = \frac{225.0 + 269.9}{2}$$

Accepted Answer

$$247.45$$

Question 4

Which of the following is most sensitive to extreme values?

A) Range
B) Mean
C) Mode
D) Variance

Accepted Answer

Range

Question 5

A sample of commute times from Boston has a mean of 38 minutes and a standard deviation of 12 minutes. Use the range rule of thumb to identify significantly high and low values. Is a commute time of 55 minutes significantly high?

$$	ext{Significantly high if} \u003e 	ext{mean} + 2 	imes 	ext{std dev}$$

Accepted Answer

No, because it is within two standard deviations of the mean.

Question 6

If all the values in a data set are identical, what will the standard deviation be?

A) Greater than zero
B) Zero

Accepted Answer

Zero

Question 7

A student scores a 96 on a test where the mean is 74 and the standard deviation is 8. What is the student's z-score?

$$z = \frac{X - \mu}{\sigma}$$

Accepted Answer

$$2.75$$

Question 8

Which of the following values cannot be a probability?

A) $$0.8
B$$) $$-0.2
C$$) $$0
D$$) $$1$$

Accepted Answer

$$-0.2$$

Question 9

A die is rolled 17 times and the number of twos that come up is tallied. If this experiment is repeated many times, what is the standard deviation for the number of twos?

$$\sigma = \sqrt{n p (1-p)}$$, where $$n=17$$, $$p=\frac{1}{6}$$

Accepted Answer

$$1.5$$

Question 10

A spinner has equal regions numbered 1 through 21. What is the probability that the spinner will stop on an even number or a multiple of 3?

$$P(	ext{even or multiple of 3}) = \frac{	ext{number of favorable outcomes}}{21}$$

Accepted Answer

$$\frac{14}{21}$$

Question 11

Which of the following is NOT a measure of variation?

A) Median
B) Range
C) Standard Deviation
D) Variance

Accepted Answer

Median

Question 12

A researcher surveys 14 newborn babies and counts the number of girls selected. The probability distribution for the number of girls is given. What is the probability of selecting exactly 6 girls?

Given: $$P(6) = 0.209$$

Accepted Answer

$$0.209$$

Question 13

On a multiple choice test with 23 questions, each question has four possible answers, only one of which is correct. For students who guess all answers, what is the mean for the number of correct answers?

$$\mu = n p$$, where $$n=23$$, $$p=\frac{1}{4}$$

Accepted Answer

$$5.75$$

Question 14

Which type of graph depicts categorical data as slices of a circle?

A) Pie chart
B) Dot plot
C) Bar graph
D) Histogram

Accepted Answer

Pie chart

Question 15

A class consists of 20 women and 15 men. If a student is randomly selected, what is the probability that the student is a woman?

$$P(	ext{woman}) = \frac{20}{35}$$

Accepted Answer

$$0.57$$

Question 16

Which of the following is a measure of center?

A) Median
B) Variance
C) Range
D) Frequency table

Accepted Answer

Median

Question 17

A normal distribution has what kind of shape?

A) Bell
B) Rectangle
C) Skewed
D) Polygon

Accepted Answer

Bell

Question 18

Which of the following is NOT part of the Five-Number Summary?

A) Mean
B) Median
C) Minimum
D) Maximum

Accepted Answer

Mean

Question 19

A bag contains 5 red balls and 7 blue balls. If two balls are drawn without replacement, what is the probability that both are red?

$$P(	ext{both red}) = \frac{5}{12} 	imes \frac{4}{11}$$

Accepted Answer

$$\frac{20}{132}$$

Question 20

Which of the following is the best description of the complement of an event?

A) All outcomes not in the event
B) All outcomes in the event
C) The probability of the event
D) The mean of the event

Accepted Answer

All outcomes not in the event

Comprehensive Guidance for Elementary Statistics Practice Exam (MAT 170, Triton College)

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