Stats Practice for Unit 2 Exam

1.

Open Ended

30 sec

1 pt

Rachel scored 670 on the analytic portion of the GRE (Graduate Record Exam). GRE scores are Normally distributed with a mean of 600 and a standard deviation of 30. How many standard deviations is Rachel's score above the mean?

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Answer explanation

2.33

2.

Open Ended

30 sec

1 pt

For -1.65 < z < 1.75, which one of the following graphs best represents the correct shaded area or proportion?

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Answer explanation

One with middle shaded

3.

Open Ended

30 sec

1 pt

Using the Standard Normal Table, what proportion of observations on the standard Normal curve satisfy -1.65 < z < 1.75?

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Answer explanation

0.9104

4.

Open Ended

30 sec

1 pt

Using the Standard Normal Table, what is the z-score with 0.9345 to its left?

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Answer explanation

1.51

5.

Open Ended

30 sec

1 pt

How many standard deviations above and below the mean do the quartiles of any Normal distribution lie? (Use the standard Normal distribution to find Q1 and Q3 for z-scores.)

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Answer explanation

0.67

6.

Open Ended

30 sec

1 pt

The Weschler Adult Intelligence Scale (WAIS) is the most common "IQ" test. The scale of scores is approximately Normal with a mean of 100 and a standard deviation of 15. What proportion of adults have an IQ less than 90? (Draw and label the Normal curve and use the Standard Normal Table.)

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Answer explanation

0.2514

7.

Open Ended

30 sec

1 pt

The Weschler Adult Intelligence Scale (WAIS) is the most common "IQ" test. The scale of scores is approximately Normal with a mean of 100 and a standard deviation of 15. What is the probability that a randomly selected adult will have an IQ greater than 140?

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Answer explanation

0.0038

8.

Open Ended

30 sec

1 pt

The Weschler Adult Intelligence Scale (WAIS) is the most common "IQ" test. The scale of scores is approximately Normal with a mean of 100 and a standard deviation of 15. What is the probability that a randomly selected adult will have an IQ between 130 and 140?

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Answer explanation

0.0190

9.

Open Ended

30 sec

1 pt

The Weschler Adult Intelligence Scale (WAIS) is the most common "IQ" test. The scale of scores is approximately Normal with a mean of 100 and a standard deviation of 15. Above what value are 20% of all IQ scores?

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Answer explanation

112.6

10.

Open Ended

30 sec

1 pt

Which of the following intervals corresponds to the smallest area under a Normal curve? Q1 to Q3 μ to μ + 3σ Q1 to μ + 2σ μ - σ to Q3

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Answer explanation

μ to μ + 3σ

11.

Open Ended

30 sec

1 pt

Which of the following is a parameter? The proportion of voters in a national sample of 1500 who say they will vote for the incumbent president The mean GPA of all incoming freshmen at a state university The standard deviation of the weights of a sample of National League Football players The median income of a sample of 300 university professors

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Answer explanation

The mean GPA of all incoming freshmen at a state university

12.

Fill in the Blank

30 sec

1 pt

The sampling distribution of x̄ gives _______ from all possible samples of the same size from the same population.

13.

Open Ended

30 sec

1 pt

Suppose we take all possible samples of the same size from a population and for each sample, we compute x̄. Will the mean of these x̄ values will be exactly equal to the mean of the population (μ) from which the samples were taken?

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Answer explanation

Yes

14.

Open Ended

30 sec

1 pt

Suppose we take all possible samples of the same size from a population and for each, we compute x̄. Will the standard deviation of these x̄ values will be less than or equal to the standard deviation of the population from which the samples were taken?

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Answer explanation

Yes

15.

Open Ended

30 sec

1 pt

According to the Central Limit Theorem, for random samples, what is the approximate shape of the sampling distribution of x̄ when the population distribution is non-Normal?

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Answer explanation

Approximately Normal if the sample size is large

16.

Open Ended

30 sec

1 pt

Suppose we have a very right skewed population distribution where μ = 80 and σ = 20. For random samples of size n = 100, what is the mean of the sampling distribution of x̄?

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Answer explanation

= to 80

17.

Open Ended

30 sec

1 pt

Suppose we have a very right skewed population distribution where μ = 80 and σ = 20. For random samples of size n = 100, what is the standard deviation of the sampling distribution of x̄?

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Answer explanation

Less than 20

18.

Open Ended

30 sec

1 pt

Suppose we have a very right skewed population distribution where μ = 80 and σ = 20. For random samples of size n = 100, what is the shape of the sampling distribution of x̄?

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Answer explanation

Approximately Normal

19.

Open Ended

30 sec

1 pt

For small random samples from a Normal population distribution, the shape of the sampling distribution of x̄ is...

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Answer explanation

Normal

20.

Open Ended

30 sec

1 pt

What is the advantage of reporting the average of several measurements rather than the result of a single measurement?

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Answer explanation

The average of several measurements is more likely to be close to the true mean than the result of a single measurement.

21.

Open Ended

30 sec

1 pt

What is the purpose of a statistical control chart?

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Answer explanation

To distinguish between natural and unnatural variation.

22.

Open Ended

30 sec

1 pt

A manufacturing process produces bags of cookies. The weights of these bags are known to be Normally distributed and should have a mean of μ = 15.0 ounces with a standard deviation of σ = 0.4 ounces. In order to monitor the process, four bags are selected periodically and their average weight (x̄) is computed. What is the parameter of interest?

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Answer explanation

The mean weight of all bags of cookies produced by this manufacturing process.

23.

Open Ended

30 sec

1 pt

A manufacturing process produces bags of cookies. The weights of these bags are known to be Normally distributed and should have a mean of μ = 15.0 ounces with a standard deviation of σ = 0.4 ounces. In order to monitor the process, four bags are selected periodically and their average weight (x̄) is computed. In order to construct an x̄-chart for this process, what number should be used as the center line?

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Answer explanation

15

24.

Open Ended

30 sec

1 pt

A manufacturing process produces bags of cookies. The weights of these bags are known to be Normally distributed and should have a mean of μ = 15.0 ounces with a standard deviation of σ = 0.4 ounces. In order to monitor the process, four bags are selected periodically and their average weight (x̄) is computed. What is the upper limit of the control chart for this process?

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Answer explanation

15.6

25.

Open Ended

30 sec

1 pt

A manufacturing process produces bags of cookies. The weights of these bags are known to be Normally distributed and should have a mean of μ = 15.0 ounces with a standard deviation of σ = 0.4 ounces. In order to monitor the process, four bags are selected periodically and their average weight (x̄) is computed. What is the lower limit of the control chart for this process?

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Answer explanation

14.4

26.

Open Ended

30 sec

1 pt

What is the symbol for the sample mean?

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Answer explanation

x̄

27.

Open Ended

30 sec

1 pt

What is the symbol for standard deviation?

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Answer explanation

s

28.

Open Ended

30 sec

1 pt

What do we use to estimate μ?

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Answer explanation

x̄

29.

Open Ended

30 sec

1 pt

An administrator in a very large company wants to estimate the mean level of nitrogen oxides (NOX) emitted in the exhaust of a particular car model in their very large fleet of cars. Historically, nitrogen oxide levels have been known to be Normally distributed with a standard deviation of 0.15 g/ml. What is the parameter of interest that the administrator wants to estimate?

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Answer explanation

The mean level of nitrogen oxide of all cars of a particular model in the very large fleet.

30.

Open Ended

30 sec

1 pt

An administrator in a very large company wants to estimate the mean level of nitrogen oxides (NOX) emitted in the exhaust of a particular car model in their very large fleet of cars. Historically, nitrogen oxide levels have been known to be Normally distributed with a standard deviation of 0.15 g/ml. What statistic is used to estimate the parameter of interest?

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Answer explanation

The mean level of nitrogen oxide of a sample of cars of a particular model in the very large fleet.

31.

Open Ended

30 sec

1 pt

Can statistical inference can be defined as making generalizations about the population based on sample data.

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Answer explanation

Yes

32.

Open Ended

30 sec

1 pt

A study of child preferences for milk chocolate was performed. Based on sample results, researchers were 95% confident that the proportion of children that liked milk chocolate was between 0.75 and 0.93. What type of inference is being used?

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Answer explanation

Interval estimation

33.

Open Ended

30 sec

1 pt

Based on sample results, researchers estimate that μ, the mean height of all female students in a university, is 64 inches. What type of inference is being used?

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Answer explanation

Point estimation

34.

Open Ended

30 sec

1 pt

Is point estimation is a form of statistical inference in which, based on the sample data, we estimate the unknown parameter of interest using a range of plausible values?

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Answer explanation

No

35.

Open Ended

30 sec

1 pt

A recent study claimed that half of all college students "drink to get drunk" at least once in a while. Believing that the true proportion is much lower, the College Alcohol Study interviews an SRS of 14,941 college students about their drinking habits and finds that 7,352 of them occasionally "drink to get drunk". What type of statistical inference is this?

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Answer explanation

Hypothesis testing

36.

Open Ended

30 sec

1 pt

What is the t* associated with 98% confidence and df = 37?

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Answer explanation

2.457

37.

Fill in the Blank

30 sec

1 pt

In confidence interval estimation, we use a confidence interval to estimate ________

38.

Open Ended

30 sec

1 pt

An administrator in a very large company wants to estimate the mean level of nitrogen oxides (NOX) emitted in the exhaust of a particular car model in their very large fleet of cars. Historically, nitrogen oxide levels have been known to be Normally distributed. A 98% confidence interval estimate for the mean nitrogen oxide level was computed. What do we hope to find in this confidence interval?

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Answer explanation

The value of μ, the mean level of nitrogen oxides emitted by all cars of a particular model in their fleet.

39.

Open Ended

30 sec

1 pt

An administrator in a very large company wants to estimate the mean level of nitrogen oxides (NOX) emitted in the exhaust of a particular car model in their very large fleet of cars. Historically, nitrogen oxide levels have been known to be Normally distributed. The correct computation of the 98% confidence interval estimate is (0.87 g/ml, 0.97 g/ml). Which of the following is a correct interpretation of this 98% confidence interval?

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Answer explanation

We are 98% confident that the value of the mean nitrogen oxide level, μ, for all cars of a particular model is between 0.87 g/ml and 0.97 g/ml.

40.

Fill in the Blank

30 sec

1 pt

The t-distribution with 6 degrees of freedom has _____ than the standard normal distribution

41.

Open Ended

30 sec

1 pt

Suppose the 95% confidence interval estimate for the mean monthly cost for Internet service for all Internet users is ($19.90, $21.90). Which of the following is a correct interpretation of this 95% confidence interval?

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Answer explanation

We are 95% confident that the mean monthly cost for Internet service paid by all Internet users is between $19.90 and $21.90.

42.

Open Ended

30 sec

1 pt

The purpose of a confidence interval is to provide...

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Answer explanation

Plausible values that a parameter could take

43.

Open Ended

30 sec

1 pt

The BYU Testing Center is known for being the location with the most prayers said per capita. Researchers asked a random sample of 47 BYU students to estimate the number of prayers they said in the BYU Testing Center last semester. The researchers are willing to consider these 47 BYU students as an SRS from the population of all BYU students. Researchers plan to use these data to estimate the mean number of prayers said by students last semester in the BYU Testing Center with 99% confidence. Suppose the confidence interval turned out to be (8.001, 13.829). What is an appropriate interpretation of this interval?

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Answer explanation

We are 99% confident that the true mean number of prayers said in the BYU Testing Center by all BYU students last semester is between 8.001 and 13.829 prayers.

44.

Open Ended

30 sec

1 pt

The weekly oral dosage of anabolic steroids was measured on a sample of 20 body builders. A 95% confidence interval estimate for the average weekly oral dose of anabolic steroids obtained from these results was 152 mg to 194 mg. Which one of the following is a correct interpretation of this confidence interval?

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Answer explanation

We are 95% confident that the average weekly dose of anabolic steroids used by all body builders is between 152 mg. and 194 mg.

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