# Stat 201 midterm exam 40/40

•Question 1

3 out of 3 points

Which is a reason for using a log scale for time series data?

.

It helps compare growth in time series of dissimilar magnitude

.

It helps compare growth in time series of dissimilar magnitude

General business audiences find it easier to interpret a log scale

On a log scale, equal distances represent equal dollar amounts

The axis labels are usually easier to read in log units

•Question 2

3 out of 3 points

We would associate the term inferential statistics with which task?

.

Estimating unknown parameters

.Making visual displays of data

Estimating unknown parameters

Describing a sample of data

Tabulating a survey

•Question 3

3 out of 3 points

A frequency histogram should be computed from which type of data?

.

Quantitative data

.

Quantitative data

Categorical data

Nominal level data

Ordinal data

•Question 4

3 out of 3 points

The number of male babies in a sample of 10 randomly chosen babies is a:

.

binomial random variable

.continuous random variable

Poisson random variable

binary random variable

binomial random variable

•Question 5

3 out of 3 points

A study is under way in Yosemite National Forest to determine the adult height of American pine trees. Specifically, the study is attempting to determine what factors aid a tree in reaching heights greater than 60 feet tall. It is estimated that the forest contains 25,000 adult American pines. The study involves collecting heights from 250 randomly selected adult American pine trees and analyzing the results. Identify the sample in the study.

.

The 250 randomly selected adult American pine trees.

.

The 250 randomly selected adult American pine trees.

The 25,000 adult American pine trees in the forest.

All the adult American pine trees taller than 60 feet.

All American pine trees, of any age, in the forest.

•Question 6

3 out of 3 points

An investment firm rates bonds for AardCo Inc. as “B+” while bonds of Deva Corp. are rated “AA.” Which level of measurement would be appropriate for such data?

.

Ordinal

.Nominal

Ordinal

Interval

Ratio

•Question 7

3 out of 3 points

Researchers are concerned that the weight of the average American school child is increasing implying, among other things, that children’s clothing should be manufactured and marketed in larger sizes. If X is the weight of school children sampled in a nationwide study, then X is an example of

.

a continuous random variable.

.a categorical random variable.

a discrete random variable.

a continuous random variable.

a parameter.

•Question 8

3 out of 3 points

When comparing data measured by substantially different scales, we must use

.

standardized data values.

.

standardized data values.

standardized data scales.

standardized data variations.

standardized data scores.

•Question 9

3 out of 3 points

A company has 2 machines that produce widgets. An older machine produces 23% defective widgets, while the new machine produces only 8% defective widgets. In addition, the new machine produces 3 times as many widgets as the older machine does. Given that a widget was produced by the new machine, what is the probability it is not defective?

.

0.92

.0.06

0.50

0.92

0.94

•Question 10

3 out of 3 points

Which is least likely to be regarded as a ratio variable?

.

A critic’s rating of a restaurant on a 1 to 4 scale

.

A critic’s rating of a restaurant on a 1 to 4 scale

Automobile exhaust emission of nitrogen dioxide (milligrams per mile)

Number of customer complaints per day at a cable TV company office

Cost of an e-Bay purchase

•Question 11

3 out of 3 points

Based on a survey of 400 students in a university in which 20 percent indicated that they were business majors. The university student newspaper reported that “20 percent of all the students at the university are business majors.” This report is an example of

.

statistical inference.

.a sample.

a population.

statistical inference.

descriptive statistics.

•Question 12

3 out of 3 points

“Bob must be rich. He’s a lawyer, and lawyers make lots of money.” This statement best illustrates which fallacy?

.

Generalizing from an average to an individual

.Using poor survey methods

Confusing significance with importance

Unconscious bias

Generalizing from an average to an individual

•Question 13

3 out of 3 points

In a certain city, 5 percent of all drivers have expired licenses, 10 percent have an unpaid parking ticket, and 1 percent have both an expired license and an unpaid parking ticket. Are these events independent?

.

No

.

No

Yes

Can’t tell from given information

•Question 14

3 out of 3 points

Retailers are always interested in determining why a customer selected their store to make a purchase. A sporting goods retailer conducted a customer survey to determine why its customers shopped at the store. The results are shown in the bar chart below. What proportion of the customers responded that they shopped at the store because of the merchandise or the convenience?

.

65%

.35%

50%

65%

85%

•Question 15

3 out of 3 points

Which of the following is true with respect to the binomial distribution?

.

The binomial distribution tends to be more symmetric as p approaches 0.5.

.As the sample size increases, the expected value of the random variable decreases.

The binomial distribution becomes more skewed as the sample size is increased for a given probability of success.

The binomial distribution tends to be more symmetric as p approaches 0.5.

In order for the binomial distribution to be skewed, the sample size must be quite large.

•Question 16

3 out of 3 points

Based on the empirical rule we can assume that all distributions have approximately 95 percent of the values within ± 2 standard deviations of the mean.

. True

. True

False

•Question 17

3 out of 3 points

The random variable X

is the number of shots it takes before you make the first free throw in basketball. Assuming the probability of success (making a free throw) is constant from trial to trial, what type of distribution does X

follow?

.

Geometric

.Binomial

Poisson

Hypergeometric

Geometric

•Question 18

3 out of 3 points

Which is not considered a deceptive graphical technique?

.

Axis demarcations

.Nonzero origin

Elastic graph proportions

Dramatic title

Axis demarcations

•Question 19

3 out of 3 points

We would use a pivot table to:

.

cross-tabulate frequencies of occurrence of two variables

.

cross-tabulate frequencies of occurrence of two variables

rotate the data around a central point

establish cause-and-effect between X and Y

display the data in a 3D scatter plot

•Question 20

3 out of 3 points

The expected value of a discrete random variable E(X) is the sum of all X values weighted by their respective probabilities.

. True

. True

False

•Question 21

3 out of 3 points

A die is rolled. If it rolls to a 1, 2, or 3 you win $2. If it rolls to a 4, 5, or 6 you lose $1. Find the expected winnings.

.

$0.50

.

$0.50

$3.00

$1.50

$1.00

•Question 22

3 out of 3 points

If cars arrive to a service center randomly and independently at a rate of 5 per hour on average, what is the probability that exactly 5 cars will arrive during a given hour?

.

0.1755

.

0.1755

0.6160

0.1277

Essentially zero

•Question 23

3 out of 3 points

A random variable is binomially distributed with n = 16 and pi = .40. The expected value and standard deviation of the variables are:

.

6.40 and 1.96

.2.00 and 1.24

4.80 and 4.00

6.40 and 1.96

2.00 and 1.20

•Question 24

3 out of 3 points

A study was recently done in which the brand preference for breakfast cereal was analyzed against the gender of the shopper. The study consisted of 200 male shoppers and 300 female shoppers. Three different cereal brands were considered: A, B, and C. A total of 250 female shoppers preferred brand A, 25 female shoppers preferred brand C. The number of female shoppers that preferred brand B was:

.

25.

.

25.

100.

75.

50.

•Question 25

3 out of 3 points

How many ways can we choose three items at random without replacement from five items (A, B, C, D, E) if the order of the selected items is not important?

.

10

.60

120

10

24

•Question 26

3 out of 3 points

On a particular day, 112 of 280 passengers on a particular DTW-LAX flight used the e-ticket check-in kiosk to obtain boarding passes. In a random sample of eight passengers, use the binomial model to find the approximate hypergeometric probability that four will have used the e-ticket check-in kiosk to obtain boarding passes.

.

.2322

.

.2322

.8263

2926

.5613

•Question 27

3 out of 3 points

A major retail store has studied customer behavior and found that the distribution of time customers spend in a store per visit is symmetric with a mean equal to 17.3 minutes. Based on this information, which of the following is true?

.

The median is approximately 17.3 minutes.

.The distribution is bell-shaped.

The median is to the right of the mean.

The median is approximately 17.3 minutes.

The median is to the left of the mean.

•Question 28

3 out of 3 points

Assume P(A) =

0.6, P(B) = 0.7, and P(A and B) = 0.42, which means that events A and B are independent of each other.

. True

. True

False

•Question 29

3 out of 3 points

Suppose 10 students are enrolled in a class and the probability of at least 8 showing up on a given day is 90 percent. Then the probability of 7 or fewer showing that day is 10 percent.

. True

. True

False

•Question 30

3 out of 3 points

In a recent study of the sales prices of houses in a Midwestern city, the mean sales price has been reported to be $167,811 while the median sales price was $155,600. From this information, you can determine that the data involved in the study are left-skewed.

. False

.True

False

•Question 31

3 out of 3 points

Ten percent of the corporate managers at Axolotl Industries majored in humanities. What is the expected number of managers to be interviewed until finding the first one with a humanities major?

.

10

.15

20

10

17

•Question 32

3 out of 3 points

If the number of defective items selected at random from a parts inventory is considered to follow a binomial distribution with n = 50 and p =

0.10, the expected number of defective parts is:

.

5.

.

5.

approximately 2.24.

more than 10.

0.5.

•Question 33

3 out of 3 points

The manager of Ardmore Pharmacy knows that 25 percent of the customers entering the store buy prescription drugs, 65 percent buy over-the-counter drugs, and 18 percent buy both types of drugs. What is the probability that a randomly selected customer will buy at least one of these two types of drugs?

.

0.72

.0.90

0.85

0.72

0.65

•Question 34

3 out of 3 points

When constructing charts, the following is plotted at the class midpoints:

.

percentage polygons.

.frequency histograms.

percentage polygons.

cumulative relative frequency ogives.

All of the above.

•Question 35

3 out of 3 points

When you send out a resume, the probability of being called for an interview is .20. What is the expected number of resumes you send out until you get the first interview?

.

5

.

5

7

10

12

•Question 36

3 out of 3 points

What type of probability distribution will most likely be used to analyze the number of chocolate chip parts per cookie in the following problem? The quality control manager of Marilyn’s Cookies is inspecting a batch of chocolate chip cookies. When the production process is in control, the average number of chocolate chip parts per cookie is 6.0. The manager is interested in analyzing the probability that any particular cookie being inspected has fewer than 5.0 chip parts.

.

Poisson distribution.

.binomial distribution.

Poisson distribution.

hypergeometric distribution.

none of the above.

•Question 37

3 out of 3 points

The employees of a company were surveyed on questions regarding their educational background and marital status. Of the 600 employees, 400 had college degrees, 100 were single, and 60 were single college graduates. The probability that an employee of the company does not have a college degree is:

.

0.33

.0.10

0.33

0.67

0.75

•Question 38

3 out of 3 points

The following probability distribution has been assessed for the number of accidents that occur in a Midwestern city each day:

AccidentsProbability

00.25

10.20

20.30

30.15

40.10

The probability of having less than 2 accidents on a given day is:

.

0.45.

.0.30.

0.75.

0.45.

0.25.

•Question 39

3 out of 3 points

One of the characteristics of the binomial distribution is that the probability of success for each trial depends on whether the previous trial was a success or not.

. False

.True

False

•Question 40

3 out of 3 points

Exam scores in a small class were 10, 10, 20, 20, 40, 60, 80, 80, 90, 100, 100. For this data set, which statement is incorrect concerning measures of center?

.

The geometric mean is 35.05

.The median is 60.00

The mode is not helpful

The 5 percent trimmed mean would be awkward

The geometric mean is 35.05

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