20-hw10 - Stat 20: solutions to homework 10 Michael Lugo...

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Unformatted text preview: Stat 20: solutions to homework 10 Michael Lugo November 22, 2010 1 Chapter 26, #2 (a) The box model is that the data are like 3800 draws at random with replacement from a box containing 1s and 0s, where the proportion of 1s is p . (b) The null hypothesis is that p = 18 / 38; the alternative hypothesis is that p > 18 / 38. (c) The expected number of reds is 1800. The standard error of the number of reds is √ 3800 × p 18 / 38 × 20 / 38 ≈ 31. Thus we have z = (1890- 1800) / 31 ≈ 2 . 9 and P ≈ . 002. (d) Yes, there are too many reds. 2 Chapter 26, # 4 The null hypothesis that the TA assumes here is that the scores in his section are like 30 draws at random from a box containing all 900 scores. The null hypothesis gives an average of 63 and an SD of 20. The standard error of the average of 30 scores is therefore 20 / √ 30 ≈ 3 . 65. So we have z = (55- 63) / 3 . 65 ≈ - 2 . 2, and P ≈ . 01. The answer is no....
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This note was uploaded on 07/21/2011 for the course STAT 20 taught by Professor Staff during the Spring '08 term at Berkeley.

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20-hw10 - Stat 20: solutions to homework 10 Michael Lugo...

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