Random sample of size n from an infinite population

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Unformatted text preview: p(1 - p) n sp = ˆ If x is the mean of a random sample of size n from an infinite population with mean µ and standard deviation s , then: µx = µ sx = s n -4- 2010 AP® STATISTICS FREE-RESPONSE QUESTIONS (Form B) (III) Inferential Statistics Standardized test statistic: statistic - parameter standard deviation of statistic Confidence interval: statistic ± (critical value ) ∑ (standard deviation of statistic ) Single-Sample Sample Mean Standard Deviation of Statistic s n Sample Proportion p(1 - p) n Statistic Two-Sample Standard Deviation of Statistic Statistic Difference of sample means 2 s1 s2 +2 n1 n2 Special case when s1 = s 2 s 1 1 + n1 n2 p1 (1 - p1 ) p2 (1 - p2 ) + n1 n2 Difference of sample proportions Special case when p1 = p2 p (1 - p ) Chi-square test statistic = Â -5- 1 1 + n1 n2 (observed - expected )2 expected 2010 AP® STATISTICS FREE-RESPONSE QUESTIONS (Form B) STATISTICS SECTION II Part A Questions 1-5 Spend about 65 minutes on this part of the exam. Percent of Section II score—75 Directions: Show all your work. Indicate clearly the methods you use, because you will be scored on the correctness of your methods as well as on the accuracy and completeness of your results and explanations. 1. As a part of the United States Department of Agriculture’s Super Dump cleanup efforts in the early 1990s, various sites in the country were targeted for cleanup. Three of the targeted sites—River X, River Y, and River Z—had become contaminated with pesticides because they were located near abandoned pesticide dump sites. Measurements of the concentration of aldrin (a commonly used pesticide) were taken at twenty randomly selected locations in each river near the dump sites. The boxplots shown below display the five-number summaries for the concentrations, in parts per million (ppm) of aldrin, for the twenty locations that were sampled in each of the three rivers. (a) Compare the distributions of the concentration of aldrin among the three rivers. (b) The twenty concentration...
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