AnswersAZ-Common Core Algebra II BStatistical Inferences

Statistical Inferences — Unit test Answers

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The president of the math club is conducting a survey to see where the twelfth-grade class wants to go on their field trip. Instead of asking the whole class, she surveys only the twelfth-grade members of the math club. She records their choices and plans to present the results to the school principal. What type of sampling did she use?

A
systematic random sampling
B
simple random sampling
C
stratified sampling
D
convenience sampling
2
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Johnni guessed on all 8 questions of a multiple-choice quiz. Each question has 4 answer choices. What is the probability that she got exactly 3 questions correct? Round the answer to the nearest thousandth.

Question illustration
A
0.004
B
0.208
C
0.422
D
0.792
3

A utility company hires pollsters to knock on random doors in different parts of town to survey residents about the cost of their electric bill. Would this study be biased? Why or why not?

A
No, it is not biased. All residents of the town will have the opportunity to respond.
B
Yes, it is biased. Some of the residents who are surveyed may not want to respond to someone who knocks at their door.
C
No, it is not biased. All residents who are surveyed will want to respond.
D
Yes, it is biased. Only certain parts of the town were surveyed.
4

A simple random sample of size n is drawn from a normally distributed population, and the mean of the sample is , while the standard deviation is s. What is the 90% confidence interval for the population mean? Use the table below to help you answer the question.Confidence Level90%95%99%z*-score1.6451.962.58

Question illustration
A
x Overbar plus-or-minus StartFraction 0.90 times s Over StartRoot n EndRoot EndFraction
Option A
B
x Overbar plus-or-minus StartFraction 1.645 times s Over StartRoot n EndRoot EndFraction
Option B
C
x Overbar plus-or-minus StartFraction 1.96 times s Over StartRoot n EndRoot EndFraction
Option C
D
x Overbar plus-or-minus StartFraction 2.58 times s Over StartRoot n EndRoot EndFraction
Option D
5

A gymnastics coach records the scores of a gymnast and develops the probability distribution below. What is the probability the gymnast scores a 9 or 9.5?Probability DistributionGymnastics Score: XProbability: P(X)50.025.50.0260.066.50.170.167.50.1480.188.50.189?9.50.02

A
0.02
B
0.04
C
0.12
D
0.14
6

The times of all 15 year olds who run a certain race are approximately normally distributed with a given mean = 18 sec and standard deviation = 1.2 sec. What percentage of the runners have times less than 14.4 sec?

Question illustration
A
0.15%
B
0.30%
C
0.60%
D
2.50%
7

Laila guesses on all 20 questions of a multiple-choice test. Each question has 4 answer choices. What is the probability of a success and a failure for this experiment?

A
;
Option A
B
;
Option B
C
;
Option C
D
;
Option D
8

Weston completed a hypothesis test and found that he could not reject the null hypothesis. Which of the following is a valid reason for his conclusion?

A
The z-statistic is less than 0.
B
The z-statistic lies in the critical region.
C
The z-statistic is greater than 0.
D
The z-statistic lies outside the critical region.
9

Car insurance companies want to keep track of the average cost per claim. The current data in use for Auto Insurance R Us is an average of $2,200 for each claim with a standard deviation of $500. With this average, the company can stay competitive with rates but not lose money. However, the statistician for the company believes that the cost of the average claim has increased. He pulled 40 recent claims and found the average to be $2,350. Which most restrictive level of significance would suggest that the company should raise rates? Upper-Tail Valuesa5%2.5%1%Critical z-values1.651.962.58

A
1%
B
2.5%
C
5%
D
10%
10

The histogram below shows the estimated monthly salaries of company employees with different years of experience. How might the graph be misleading?

Question illustration
T
The scale on the y-axis overemphasizes the difference in salaries between different experience levels.
T
The scale on the y-axis underemphasizes the difference in salaries between different experience levels.
T
The scale on the x-axis overemphasizes the difference in salaries between different experience levels.
T
The scale on the x-axis underemphasizes the difference in salaries between different experience levels.
11

When finding the margin of error for the mean of a normally distributed population from a sample, what is , assuming a confidence level of 74%?

Question illustration
A
0.13
B
0.26
C
0.74
D
0.87
12

A scientist calculated the mean and standard deviation of a data set to be and . She then found that she was missing one data value from the set. She knows that the missing data value was exactly 3 standard deviations away from the mean. What was the missing data value?

Question illustration
A
129
B
147
C
360
D
369
13

Vladimir rolls a six-sided number cube 36 times. If getting a 3 is a success, what is the probability of a success?

A
One-sixth
Option A
B
One-third
Option B
C
Two-thirds
Option C
D
Five-sixths
Option D
14

Which set of population data is the least dispersed from its mean?

A
2, 3, 2, 9
B
4, 0, 4, 0
C
6, 2, 2, 2
D
9, 3, 5, 3
15

Voluntary sampling is one type of sampling method that is not probability based. This means that

A
each member of a population is equally likely to be chosen for the survey.
B
the results of the survey cannot reliably be extended and generalized.
C
the likelihood of a member of the population volunteering to be surveyed is not probable.
D
the results of the survey are not mathematically probable.
16

The graph below shows the amount of time Misha spent outside over a 30-day period. How might the graph be considered misleading?

Question illustration
A
The x-scale is different from the y-scale.
B
The x-interval makes the data appear skewed.
C
The y-scale is too large for the data set.
D
The y-interval shows exponential increase rather than linear increase.
17

A local newspaper compiles data on the number of days, X, people in a neighborhood receive the newspaper. The probability distribution for the data is shown in the table below. What is the probability that a randomly chosen person receives the newspaper at least one day per week?

Question illustration
A
16%
B
33%
C
41%
D
83%
18

The histogram below shows the number of weeks Jimmy spent different amounts of money to fill the gas tank in his car. If the graph is redrawn so that the scale on the y-axis begins with zero, which aspect of the graph will change the most?

Question illustration
A
The difference in the heights of the bars will not appear as great.
B
The difference in the heights of the bars will be more pronounced.
C
The graph will appear more skewed to the left.
D
The graph will appear more skewed to the right.
19

The number of absences for one week for all students at a high school were compiled, and the probability distribution below was created. What is the probability in any given week that a randomly selected student will be absent no more than one day?Probability DistributionDays Absent: XProbability: P(X)00.7810.1420.0330.014050.04

A
0.08
B
0.14
C
0.78
D
0.92
20

The histogram below shows the average number of days per year in 117 Oklahoma cities where the high temperature was greater than 90 degrees Fahrenheit.Which is an accurate comparison?

Question illustration
A
The mean is likely greater than the median because the data is skewed to the right.
B
The mean is likely greater than the median because the data is skewed to the left.
C
The median is likely greater than the mean because the data is skewed to the right.
D
The median is likely greater than the mean because the data is skewed to the left.

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