
Concept explainers
Visits to Social Networking Sites The table shows the number of persons age 2 and older in any U.S. location, in millions, who visited the listed Web sites at least once in June 2013.
Rank | Web Site | Visitors |
1 | 144.7 | |
2 | 50.6 | |
3 | 39.1 | |
4 | Tumblr | 35.9 |
5 | 27.9 | |
Source: com Score Media Metrix; com Score q Search |
Use this information to determine each of the following.
(a) the mean number of visitors per site
(b) the range
(c) the standard deviation
(d) the coefficient of variation
(a)

To calculate: The Mean number of visitors per site using the following information.
Rank | Web Site | Visitor |
1 | 144.7 | |
2 | 50.6 | |
3 | 39.1 | |
4 | Tumblr | 35.9 |
5 | 27.9 |
Answer to Problem 1T
Solution:
The required mean is approximately 59.6 million
Explanation of Solution
Formula used:
Mean of n data items can be found with the formula,
Calculation:
Since, mean can be found with the formula,
Thus, mean will be:
(b)

To calculate: The range of the following data.
Rank | Web Site | Visitor |
1 | 144.7 | |
2 | 50.6 | |
3 | 39.1 | |
4 | Tumblr | 35.9 |
5 | 27.9 |
Answer to Problem 1T
Solution:
The required range is 116.8 million.
Explanation of Solution
Formula used:
Range is the difference between highest data value and lowest data value.
Calculation:
Since, range is the difference between highest data value and lowest data value
So, range
(c)

To calculate: The standard deviation of the following data.
Rank | Web Site | Visitor |
1 | 144.7 | |
2 | 50.6 | |
3 | 39.1 | |
4 | Tumblr | 35.9 |
5 | 27.9 |
Answer to Problem 1T
Solution:
The required standard deviation is 48.2 million.
Explanation of Solution
Formula used:
Standard deviation is:
Calculation:
Formula for standard deviation is:
Thus,
Now, take the square root,
(d)

To calculate: The coefficient of variation of the following data.
Answer to Problem 1T
Solution:
The coefficient of variation is approximately 80.9%.
Explanation of Solution
Formula used:
Formula for coefficient of variation is:
Calculation:
Hence, the coefficient of variation is approximately 80.9%.
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Chapter 12 Solutions
Mathematical Ideas (13th Edition) - Standalone book
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