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Chapter 2: Q. 7 (page 139)
T2.7. If the heights of American men follow a Normal distribution, and have heights between and , what is your estimate of the standard deviation of the height of American men?
(a)
(b)
(c)
(d)
(e)
The standard deviation of the height of American men is option (c).
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The distribution of heights of adult American men is approximately Normal with mean inches and standard deviation of inches. Draw a Normal curve on which this mean and standard deviation are correctly located. (Hint: Draw the curve first, locate the points where the curvature changes, then mark the horizontal axis.)
Use Table A to 铿乶d the proportion of observations from the standard Normal distribution that satis铿乪s each of the following statements. In each case, sketch a standard Normal curve and shade the area under the curve that is the answer to the question. Use your calculator or the Normal Curve applet to check your answers.
More Table A practice
(a) is between 鈭�and
(b) is between and
The weights of laboratory cockroaches follow a Normal distribution with mean grams and standard deviation grams. The figure below is the Normal curve for this distribution of weights.
Point C on this Normal curve corresponds to
(a) grams.
(c) grams.
(e) grams
(b) grams.
(d) grams.
T2.4. The figure shows a cumulative relative frequency graph of the number of ounces of alcohol consumed per week in a sample of adults. About what percent of these adults consume between and ounces per week?
(a)(b)(c)(d)(e)
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 .)
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