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Stats week 8

# Stats week 8 - Sarah Anderson Stats week 8 Exercises 2 5...

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Sarah Anderson Stats week 8 Exercises 2, 5 done(page 297) Exercises 11 done 12 (page 304 – 305) Exercise 16 (page 308) done Exercise 20 (page 310) done Exercises 26, 28 done (page 313) 2.) the confidence interval is: (40-1.64*5/9 , 40+1.64*5/9) 5.) a. \$20. It is our best estimate of the population mean. b. \$18.60 and \$21.40, found by \$20 +- 1.96(\$5/sq root of 49. About 95% of the intervals similarly constructed will include the population mean. 11.) The population mean is unknown, but the best estimate Is 20, the sample mean. 12.) ANSWER: 90% Resulting Confidence Interval for 'true mean': = [51, 69] Why??? SMALL SAMPLE, CONFIDENCE INTERVAL, NORMAL POPULATION DISTRIBUTION x-bar = Sample mean 60 s = Sample standard deviation 20 n = Number of samples 16 df = degrees of freedom 15 significant digits 1 Confidence Level 90 "Look-up" Table 't-critical value' 1.8 Look-up Table of t critical values for confidence and prediction intervals. Central two-side area = 90% with df = 15. Another Look-up method is to utilize Microsoft Excel function: TINV(probability,degrees_freedom) Returns the inverse of the Student's t-distribution 90% Resulting Confidence Interval for 'true mean': x-bar +/- ('t critical value') * s/SQRT(n) = 60 +/- 1.8 * 20/SQRT(16) = [51, 69]

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Stats week 8 - Sarah Anderson Stats week 8 Exercises 2 5...

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