Exercises

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Section 2.4 Exercises

Checkpoint 2.4.1.

Consider the following relative frequency table on hurricanes that have made direct hits on the U.S. between 1851 and 2004 (http://www.nhc.noaa.gov/gifs/table5.gif). Hurricanes are given a strength category rating based on the minimum wind speed generated by the storm. Some of the entries to the table are missing.

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Table 2.4.2. Frequency of Hurricane Direct Hits

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Category	# Direct Hits	Relative Freq.	Cum. Relative Freq.
1	109
2	72	0.2637	0.6630
3		0.2601
4	18		0.9890
5	3	0.0110	1.0000

What is the relative frequency of direct hits of category 1?
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What is the relative frequency of direct hits of category 4 or more?
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Checkpoint 2.4.3.

The number of calves that were born to some cows during their productive years was recorded. The data was entered into an R object by the name “calves”. Refer to the following R code:

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freq <- table(calves)
cumsum(freq)

##  1  2  3  4  5  6  7 
##  4  7 18 28 32 38 45

How many cows were involved in this study?
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How many cows gave birth to a total of 4 calves?
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What is the relative frequency of cows that gave birth to at least 4 calves?
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