Concept explainers
(a)
To describe: the shape, center, and spread of the distribution of shark lengths
(a)
Answer to Problem 63E
Shape: symmetric and roughly bell-shaped.
Center:
Spread: standard deviation is 2.5499
Explanation of Solution
Given:
18.7 | 12.3 | 18.6 | 16.4 | 15.7 | 18.3 | 14.6 | 15.8 | 14.9 | 17.6 | 12.1 |
16.4 | 16.7 | 17.8 | 16.2 | 12.6 | 17.8 | 13.8 | 12.2 | 15.2 | 14.7 | 12.4 |
13.2 | 15.8 | 14.3 | 16.6 | 9.4 | 18.2 | 13.2 | 13.6 | 15.3 | 16.1 | 13.5 |
19.1 | 16.2 | 22.8 | 16.8 | 13.6 | 131 | 15.7 | 19.7 | 18.7 | 13.2 | 16.8 |
Lengths of sharks are in feet of 44
Calculation:
Variable | N | Mean | St.Dev. | Min | M | Max | ||
Shark length | 44 | 15.586 | 2.550 | 9.40 | 13.525 | 15.75 | 17.40 | 22.80 |
Shark lengths are roughly symmetric with a peak at 16 and vary from minimum value of 9.40 feet to maximum value 22.8 feet.
Shape: symmetric and roughly bell-shaped.
Center: Mean is 15.5884 and median is 15.75
Spread: standard deviation is 2.5499
Conclusion:
Shape: symmetric and roughly bell-shaped.
Center: Mean is 15.5884 and median is 15.75
Spread: standard deviation is 2.5499
(b)
To describe: the percent of observations that fall within one, two, and three standard deviations of the mean.
(b)
Answer to Problem 63E
One standard deviations = 68.2%
Two standard deviations = 95.5%
Three standard deviations = 100%
Explanation of Solution
Calculation:
From the above output,
Mean,
Sample standard deviation,
Percent of interval
Percent of interval
Percent of interval
According to the 68-95-99.7 rule, approximately 68.2% of the data values fall within one standard deviation. 95.5% of the data values fall within two standard deviations, and 100% of the data values fall within three standard deviations of the mean.
Conclusion:
Therefore,
One standard deviations = 68.2%
Two standard deviations = 95.5%
Threestandard deviations = 100%
(c)
To construct: a Normal probability plot and interpret the plot.
(c)
Answer to Problem 63E
The pattern in the Normal probability plot is fairly linear and it is roughly normally distributed.
Explanation of Solution
Calculation:
A Normal probability plot from Minitab is shown below:
The plot is fairly linear except from one small shark and one large shark lengths, indicating that the Normal distribution is appropriate.
Conclusion:
Therefore, a Normal probability plot is plotted. The pattern in the Normal probability plot is fairly linear and it is roughly normally distributed.
(c)
To explain:whether the data are approximately Normal
(c)
Answer to Problem 63E
The data are approximately Normal
Explanation of Solution
Calculation:
Results from the parts (a), (b), and (c) indicates that shark lengths are approximately normal.
Approximately normal, because the normal probability plot was roughlynormal and the histogram were roughly bell-shaped.
Conclusion:
Therefore, the data are approximately Normal
Chapter 2 Solutions
The Practice of Statistics for AP - 4th Edition
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