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Unformatted text preview: 5E practice problems for exam 2 1. The normal approximation will have the same mean and standard deviation as the binomial. These are 600 (1 / 6) = 100 and p 600(1 / 6)(1 1 / 6) = 9 . 13. We want the area to left of 80, so we calculate the zscore of 80: z = 80 100 9 . 13 = 2 . 19. The table gives .0143. A normal distribution is symmetric about its mean, so the area to the right of 120 is the same as the area to the left of 80: .0143. To find the probability that at least 110 are ones, we find the zscore of 110: z = 110 100 9 . 13 = 1 . 10. From symmetry, we can use the table value for z = 1 . 10 directly (and must use it for the halftable given in the exam). This value is .1357. 2. We could calculate each zscore in one fell swoop, but it will be convenient to first calculate the mean and standard deviation of the distribution of sample means. They are 22 and 8 / 5 = 3 . 58....
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 Fall '08
 LANDRIGAN
 Binomial, Standard Deviation

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