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Chapter 2: Q 38. (page 109)
If every observation in a data set is multiplied by , the only one of the following that is not multiplied by is
(a) the mean. (d) the standard deviation.
(b) the median. (e) the variance.
(c) the IQR.
The correct option is (e).
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About what proportion of observations lie between and ?
Gas it up! (1.3) Interested in a sporty car? Worried that it might use too much gas? The Environmental Protection Agency lists most such vehicles in its 鈥渢wo-seater鈥� or 鈥渕inicompact鈥� categories. The figure shows boxplots for both city and highway gas mileages for our two groups of cars. Write a few sentences comparing these distributions.
Normal is only approximate: ACT scores Scores on the ACT test for the 2007 high school graduating class had mean and standard deviation . In all, students in this class took the test. Of these, had scores higher than and another had scores exactly 27. ACT scores are always whole numbers. The exactly Normal distribution can include any value, not just whole numbers. What鈥檚 more, there is no area exactly above under the smooth Normal curve. So ACT scores can be only approximately Normal. To illustrate this fact, find
(a) the percent of ACT scores greater than .
(b) the percent of ACT scores greater than or equal to .
(c) the percent of observations from the distribution that are greater than 27. (The percent greater than or equal to is the same, because there is no area exactly over .)
Cool pool? Coach Ferguson uses a thermometer to measure the temperature (in degrees Celsius) at different locations in the school swimming pool.
An analysis of the data yields a mean ofand a standard deviation of . Find the mean and standard deviation of the temperature readings in degrees Fahrenheit (recall that
T2.8. Which of the following is not correct about a standard Normal distribution?
(a) The proportion of scores that satisfy is .
(b) The proportion of scores that satisfy is .
(c) The proportion of scores that satisfy is .
(d) The proportion of scores that satisfy is .
(e) The proportion of scores that satisfyis .
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