Chapter 3: Problem 73
Briefly explain the empirical rule. To what kind of distribution is it applied?
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Chapter 3: Problem 73
Briefly explain the empirical rule. To what kind of distribution is it applied?
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A sample of 3000 observations has a mean of 82 and a standard deviation of 16 . Using the empirical rule, find what percentage of the observations fall in the intervals \(\bar{x} \pm 1 s, \bar{x} \pm 2 s\), and \(\bar{x} \pm 3 s\).
Answer the following questions a. The total weight of all pieces of luggage loaded onto an airplane is 12,372 pounds, which works out to be an average of \(51.55\) pounds per piece. How many pieces of luggage are on the plane? b. A group of seven friends, having just gotten back a chemistry exam, discuss their scores. Six of the students reveal that they received grades of \(81,75,93,88,82\), and 85, respectively, but the seventh student is reluctant to say what grade she received. After some calculation she announces that the group averaged 81 on the exam. What is her score?
The mean age of six persons is 46 years. The ages of five of these six persons are \(57,39,44,51\), and 37 years, respectively. Find the age of the sixth person.
Melissa's grade in her math class is determined by three 100 -point tests and a 200 -point final exam. To determine the grade for a student in this class, the instructor will add the four scores together and divide this sum by 5 to obtain a percentage. This percentage must be at least 80 for a grade of \(\mathrm{B}\). If Melissa's three test scores are 75,69 , and 87 , what is the minimum score she needs on the final exam to obtain a B grade?
According to Fair Isaac, "The Median FICO (Credit) Score in the U.S. is 723" (The Credit Scoring Site, 2009). Suppose the following data represent the credit scores of 22 randomly selected loan applicants. \(\begin{array}{lllllllllll}494 & 728 & 468 & 533 & 747 & 639 & 430 & 690 & 604 & 422 & 356 \\ 805 & 749 & 600 & 797 & 702 & 628 & 625 & 617 & 647 & 772 & 572\end{array}\) a. Calculate the values of the three quartiles and the interquartile range. Where does the value 617 fall in relation to these quartiles? b. Find the approximate value of the 30 th percentile. Give a brief interpretation of this percentile. c. Calculate the percentile rank of 533 . Give a brief interpretation of this percentile rank.
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