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# WA6 - Robert E Goode Thomas Edison State College...

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Robert E Goode Thomas Edison State College STA-201-OL010 Mentor: Steve Stutz Date: 11/04/11 Writing Assignment #6 Exercises Set 8.1 (8.4, 8.6, 8.8) 8.4 a. n=44 sum X i 2 =344 mean = sum X 1 2 /N = 334/44 =7.59 b. sampling mean is not exactly the population mean due to sampling error. Exercise 8.6 a. ơ = 2.4 ơ x = ơ x /√n = 2.4/√44 =.36 X - 2 ơ x = 6.87 X+2 ơ x =8.31 b. confidence interval: 6.87 – 8.31 c. 95.44% confident interval contains µ.

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d. depends on the sample mean 8.8 a. Mean = 129849/45 = \$2,885.53 (point estimate) Ơ x = ơ x /√n = 1350/√45 = 201.19 Mean - 2 ơ x =\$2,483.15 Mean + 2 ơ x =\$3,287.91 b. confidence interval: \$2483.15 - \$3287.91 c. Bell shaped histogram d. No, sample size is sufficient. Exercises Set 8.2 (8.24, 8.26, 8.32, 8.38) 8.24 A good typist can type 70wpm. Confidence level = 1-0.99 = 0.01 The majority of applicants type less than 70wpm. 8.26 Mean = 25, n = 36, σ = 3 and the confidence level is 95% The 95% confidence interval: Mean-Z* /√n =25+/-1.96*3/√36 ơ 24.02 – 25.98 8.32 mean = 947.38, n = 18, σ = 188 and the confidence level is 95% The 95% confidence interval for u is a. 947.38+/-1.96*188/√18 = 860.53 – 1034.23
b. 95% above interval contains the population mean. 8.38 mean= 947.38, n = 18, σ = 188 and the confidence level is 95% a. α = 1-0.90 = 0.10 Z(.05) = 1.645 The 90% confidence interval is 947.38+/-1.645*188/√18 874.49 - 1020.27 b. confidence level decreased from 95% to 90%. c.

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WA6 - Robert E Goode Thomas Edison State College...

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