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Chapter 3: Q 3.59. (page 113)
Why you use the standard deviation as a measure of variation. What is the reference point.
When using the standard deviation as a measure of variation, the mean of the data set serves as the reference point.
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Find the
a. Mean b. median c. mode
For the mean and the median, round each answer to one more decimal place than that used for the observations.
Daily Motorcycle Accidents. The Scottish Executive, Analy. tical Services Division Transport Statistics, compiles data on motor cycle accidents. During one year, the numbers of motorcycle accidents in Scotland were tabulated by day of the week for built-up roads and non-built-up roads and resulted in the following data .
a. Find the mean and median of the number of accidents for built-up roads.
The data set has size. Approximately how many observations lie within three standard deviations to either side of the mean?
Consider the following sample of exam scores, arranged in increasing order.
The sample mean and sample standard deviation of these exam scores are and , respectively.
a. Compare the percentage of the observations that actually lie within two standard deviations to either side of the mean with that given by Chebyshev's rule with
b. Repeat part (a) with
c. Interpret your results from parts (a) and (b).
Suppose you buy a new car whose advertised mileage is 25 miles per gallon (mpg). After driving your car for several months, you find that its mileage is 21.4mpg. You telephone the manufacturer and learn that the standard deviation of gas mileages for all cars of the model you bought is 1.15 mpg.
Part (a): Find the z-score for the gas mileage of your car, assuming the advertised claim is correct.
Part (b): Does it appear that your car is getting unusually low gas mileage?
The Great Gretzky. Wayne Giretzy, a retired professional hockey player, played 20 seasons in the National Hockey League (NHL), from 1980 through 1999 , S, Berry explored some of Gretaky"s accomplishmeats in "A Statistician Reads the Sports Pages" (Chanee, Vol, 16, Ne, 1. Pp. 49-54). The following table shoras the sumber of games in which Greuky played during each of has 20 seasons in the NHL.
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