EBook Problems EDA IntroVar

EBook Problems Set - The Nature of Data and Variation Problems

Problem 1

Researchers do a study on the number of cars that a person owns. They think that the distribution of their data might be normal, even though the median is much smaller than the mean. They make a p-plot. What does it look like?

• Choose one answer.

(a) It's not a straight line.

(b) It's a bell curve.

(c) It's a group of points clustered around the middle of the plot.

(d) It's a straight line.

Answer

 (a)

Problem 2

Bicycles arrive at a bike shop in boxes. Before they can be sold, they must be unpacked, assembled, and tuned (lubricated, adjusted,etc). Based on past experience, the shop manager makes the following assumptions about how long this may take: The times for each setup phase are independent The times for each phase follow a Normal curve The means and standard deviations of the times (in minutes) are as shown

Phase	Mean	SD
Unpacking	3.5	0.7
Assembly	21.8	2.4
Tuning	21.8	2.7

What are the mean and standard deviation for the total bicycle set up time?

• Choose one answer.

(a) Mean = 100 min, standard deviation = 12 min

(b) Can't be determined with the information given

(c) Mean = 37.6 min, standard deviation = 3.7 min

(d) Mean = 20 min, standard deviation = 13.69 min

Answer

 (c)

Problem 3

Let X be a random variable with mean 80 and standard deviation 12. Find the mean and the variance of the following variable: 2X-100

• Choose one answer.

(a) Mean = 100, variance = 288

(b) Mean = 60, variance = 12

(c) Mean = 160, variance = 144

(d) Mean = 60, variance = 576

Answer

 (d)

Problem 4

Let X be a random variable with mean 80 and standard deviation 12. Find the mean and the standard deviation of the following variable: X- 20

• Choose one answer.

(a) Mean = 60, standard deviation = 144

(b) Mean = 60, standard deviation = 12

(c) Mean = 80, standard deviation = 12

(d) Mean = 60, standard deviation = -8

Answer

 (b)

Problem 5

A physician collected data on 1000 patients to examine their heights. A statistician hired to look at the files noticed the typical height was about 60 inches, but found that one height was 720 inches. This is clearly an outlier. The physician is out of town and can't be contacted, but the statistician would like to have some preliminary descriptions of the data to present when the doctor returns. Which of the following best describes how the statistician should handle this outlier?

• Choose one answer.

(a) The statistician should publish a paper on the emergence of a new race of giants.

(b) The statistician should keep the data point in; each point is too valuable to drop one.

(c) The statistician should drop the observation from the analysis because this is clearly a mistake; the person would be 60 feet tall.

(d) The statistician should analyze the data twice, once with and once without this data point, and then compare how the point affects conclusions.

(e) The statistician should drop the observation from the dataset because we can't analyze the data with it.

Answer

 (c)

Problem 6

What do you expect the distribution of income in a company where fewer than half of the employees make less than the average to look like?

• Choose one answer

(a) Bimodal

(b) Skewed to the right or positively skewed

(c) Symmetrical

(d) Skewed to the left or negatively skewed

Answer

 (d)

Problem 7

Which of the following parameters is most sensitive to outliers?

• Choose one answer.

(a) Standard deviation

(b) Interquartile range

(c) Mode

(d) Median

Answer

 (a)

Problem 8

Which value given below is the best representative for the following data?

2, 3, 4, 4, 4, 4, 4, 5, 6, 7, 8, 9, 9, 9, 9, 9, 10, 11

• Choose one answer.

(a) The weighted average of the two modes or (4*5 + 9*5 )/10 = 6.5

(b) No single number could represent this data set

(c) The average of the two modes or (4 + 9) / 2 = 6.5

(d) The mean or (2 + 3 + 4 + ……+ 10 + 11)/18 = 5.9

(e) The median or (6 + 7)/2 = 6.5

Answer

 (b)

Problem 9

Suppose that the distribution of exam scores has mean = 20.5 and standard deviation = 2.5 and median = 15.0. If you double each score, determine the mean, deviation, and median of the transformed distribution.

• Choose one answer.

(a) mean = 41.0, deviation = 5.0, median = 30.0

(b) We cannot determine the statistics unless we have the actual data.

(c) mean = 20.5, deviation = 5.0, median = 15.0

(d) mean = 20.5, deviation = 2.5, median = 15.0

(e) mean = 41.0, deviation = 2.5, median = 30.0

Answer

 (a)

Problem 10

A recent housing survey was conducted to determine the price of a typical home in Glendale, CA. Glendale is mostly middle-class, with one very expensive suburb. The mean price of a house was roughly $650,000. Which of the following statements is most likely to be true?

• Choose one answer.

(a) There are about as many houses in Glendale that cost more than $650,000 than less than this amount.

(b) Most houses in Glendale cost less than $650,000.

(c) Most houses in Glendale cost more than $650,000.

(d) We need to know the standard deviation to answer this question.

Answer

 (b)

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• SOCR Home page: http://www.socr.ucla.edu

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