Please answer question #13.18 (Three Great Hitters) Chapter 13 Exercises 13.13 W
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Question
Please answer question #13.18 (Three Great Hitters) Chapter 13 Exercises 13.13 What percentage of IQ scores for rural Midwest seventh-graders are more than 100? 13.14 What percentage of all students have IQ scores below 78? None of the 74 students in our sample school had scores this low. Are you surprised at 13.15 Length of pregnancies. The length of human pregnancies from conception to birth varies accord ing to a distribution that is approxi- mately Normal with mean 266 days and standard deviation 16 days. Use the 68-95-99.7 rule to answer the fol- lowing guetin3 568 9 10 11 12 13 14 15 16 17 (a) Almost all (99.7%) pregnancies Figure 13.14 What are the mean and fall in what range of lengths? (b) How long are the longest 2.5% of curve? Exercise 13.16. all pregnancies? standard deviation of this Normal density George Brett's .390 in 1980. These batting averages cannot be compared directly because the distribution I curve. What are the 13.16 A Norma mean and standard deviation of the Normal curve in Figure 13.14? major league batting averages has 13.17 Horse pregnancies. Bigger ani. changed over the years. The distribu- mals tend to carry their young lon tions are quite symmetric and (except ger before birth. The length of horse for outliers such as Cobb, Williams, pregnancies from conception to birth and Brett) reasonably Normal. While varies according to a roughly Normal the mean batting average has been held roughly constant by rule changes and the balance between hitting and pitching, the standard deviation has dropped over time. Here are the facts: distribution with mean 336 days and standard deviation of three days. Use the 68-95-99.7 rule to answer the fol. lowing questions. (a) Between what values do the lengths of the middle 95% of all horse pregnancies fall? (b) What percentage of horse preg. nancies are less than 333 days? Mean Std. Decade 1910s 1940s 1970s .266 267 261 0371 0326 0317 13.18 Three great hitters. Three land. Compute the standard scores for the marks of baseball achievement are batting averages of Cobb, Williams, Ty Cobb's batting average of .420 in and Brett to compare how far each 1911, Ted Williams's.406 in 1941, and stood above his peers.Explanation / Answer
Standard score for Cobb = ( 0.420 - 0.266 ) / 0.0371 = 4.1509
Standard score for Williams = ( 0.406 - 0.267 ) / 0.0326 = 4.2638
Standard score for Brett = ( 0.390 - 0.261 ) / 0.0317 = 4.0694