Brase and Brase - Brief Statistics 5/e (Homework)

James Finch

Statistics, Fall 2010

Instructor: Dr. Friendly

Current Score: 19/34

Due: Wednesday, October 20, 2010 23:00 EDT

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Points

1	2	3	4	5	6
0/1	3	3/9	8	4	1/9

Total

19/34

Description

Here are some textbook questions from Brief Statistics 5/e by Charles Henry Brase and Corinne Pellillo Brase published by Brooks/Cole. Click here for a list of all of the questions coded in WebAssign.

Instructions

This demo assignment allows many submissions and allows you to try another version of the same question for practice.

1. 0/1 points All Submissions Notes Question: BBriefStat5 2.2.012.

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0/1

How does average height for boys change as boys get older? According to Physician's Handbook, the average heights at different ages are in the table below.

Age (years)	0.5	1	2	3	4	5	6	7	8	9	10
Height (inches)	26	29	33	36	39	42	45	47	50	52	54

Make a time-series graph for average height for ages 0.5 through 10 years. (Plot both points and lines.)

Flash Player version 10 or higher is required for this question.
You can get Flash Player free from Adobe's website.

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2. 3/3 points All Submissions Notes Question: BBriefStat5 3.1.004.

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1	2	3
1	1	1
4/50	1/50	4/50

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3/3

Consider the following types of data that were obtained from a random sample of 49 credit card accounts. Identify all the averages (mean, median, or mode) that can be used to summarize the data. (Select all that apply.)

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3. 3/9 points All Submissions Notes Question: BBriefStat5 3.2.009.

Question part

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1	2	3	4	5	6	7	8	9
1	0/1	0/1	0/1	0/1	0/1	0/1	1	1
2/50	1/50	1/50	1/50	1/50	1/50	1/50	3/50	2/50

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3/9

Kevlar epoxy is a material used on the NASA Space Shuttle. Strands of this epoxy were tested at the 90% breaking strength. The following data represent time to failure (in hours) for a random sample of 50 epoxy strands (Reference: R. E. Barlow, University of California, Berkeley). Let x be a random variable representing time to failure (in hours) at 90% breaking strength. Note: These data are also available for download online in HM StatSPACE^TM.

0.86	1.7	4.17	1.4	0.5	0.44	0.95	0.14	0.47	1.91
1.61	0.5	0.11	0.86	0.11	1.52	3.18	1.43	1.7	0.14
1.64	1.58	0.26	4.71	0.35	7.54	0.2	1.07	1.46	1.1
0.14	0.62	0.38	0.83	1.49	0.86	0.32	0.02	1.31	0.77
0.56	1.61	0.8	1.13	0.35	0.77	0.68	1.94	1.55	0.47

(a) Find the range. (Enter your answer to 2 decimal places.)
Your answer is correct.

(b) Use a calculator to calculate Σx and Σx².

Σx	Enter a number. 2
Σx²	Enter a number. 3

(c) Use the results of part (b) to compute the sample mean, variance, and standard deviation for the time to failure. (Enter your answers to 2 decimal places.)

x	Enter a number. 4
s²	Enter a number. 5
s	Enter a number. 6

(d) Use the results of part (c) to compute the coefficient of variation. (Enter your answer to one decimal place.)
Your answer is incorrect.

%

What does this number say about time to failure?

The standard deviation of the time to failure is just slightly smaller than the average time. The coefficient of variation says nothing about time to failure. The standard deviation of the time to failure is just slightly larger than the average time. The standard deviation is equal to the average.

Your answer is correct.

Why does a small CV indicate more consistent data, whereas a larger CV indicates less consistent data? Explain.

A small CV indicates more consistent data because the value of s in the numerator is smaller. A small CV indicates more consistent data because the value of s in the numerator is larger.

Your answer is correct.

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4. 8/8 points All Submissions Notes Question: BBriefStat5 5.1.009.

Question part

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Submissions

1	2	3	4	5	6	7	8
1	1	1	1	1	1	1	1
1/50	1/50	1/50	1/50	1/50	1/50	1/50	1/50

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8/8

5. 4/4 points All Submissions Notes Question: BBriefStat5 5.2.011.

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1	2	3	4
1	1	1	1
2/50	2/50	2/50	2/50

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4/4

You roll two fair dice, a green one and a red one. (Round your answers to three decimal places.)

(a) What is the probability of getting a sum of 6?
Your answer is correct.

(b) What is the probability of getting a sum of 4?
Your answer is correct.

Are the outcomes in (c) mutually exclusive?

Yes No

Your answer is correct.

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6. 1/9 points All Submissions Notes Question: BBriefStat5 5.2.022.

Question part

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1	2	3	4	5	6	7	8	9
1	0/1	0/1	0/1	0/1	0/1	0/1	0/1	0/1
1/50	2/50	0/50	0/50	0/50	0/50	0/50	0/50	0/50

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1/9

Are customers more loyal in the East or in the West? The following table is based on information from a recent study. The columns represent length of customer loyalty (in years) at a primary supermarket. The rows represent regions of the United States.

	Less Than 1 Year	1-2 Years	3-4 Years	5-9 Years	10-14 Years	15 or More Years	Row Total
East	32	60	59	112	77	116	456
Midwest	31	48	68	120	63	179	509
South	53	78	93	158	106	199	687
West	41	54	67	78	45	101	386
Column Total	157	240	287	468	291	595	2038

What is the probability that a customer chosen at random has the following characteristics? (Enter your answers as fractions.)

(a) has been loyal 10 to 14 years
Your answer is correct.

(b) has been loyal 10 to 14 years, given that he or she is from the East
Your answer is incorrect.

(c) has been loyal at least 10 years

(d) has been loyal at least 10 years, given that he or she is from the West

(e) is from the West, given that he or she has been loyal less than 1 year

(f) is from the South, given that he or she has been loyal less than 1 year

(g) has been loyal 1 or more years, given that he or she is from the East

(h) has been loyal 1 or more years, given that he or she is from the West

(i) Are the events from the East and loyal 15 or more years independent? Explain.

Yes. P(loyal 15 or more years) = P(loyal 15 or more years | East). No. These events cannot occur together. Yes. These events can occur together. No. P(loyal 15 or more years) ≠ P(loyal 15 or more years | East).

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Similarities and Differences in a Random Sample of 375 Married Couples
Number of Similar Preferences	Number of Married Couples
All four Three Two One None	25 135 123 61 31

0	1	2	3	4
Enter a number. 1	Enter a number. 2	Enter a number. 3	Enter a number. 4	Enter a number. 5

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Brase and Brase - Brief Statistics 5/e (Homework)

Current Score: 19/34