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Unformatted text preview: Solutions to Homework 7 Problem 7.13 a. A point estimate of the population mean number of units sold per month is ¯ x = ∑ x i n = 94 + 100 + 85 + 94 + 92 5 = 93 . b. A point estimate of the population standard deviation is s = s ∑ ( x i ¯ x ) 2 n 1 = s (94 93) 2 + · · · + (92 93) 2 5 1 = 5 . 39 . Problem 7.17 a. The total number of subscribers in the sample is 409 + 299 + 291 = 999. So the point estimate of subscribers who are bullish on the stock market is 409 999 = 0 . 41 . b. The point estimate of subscribers who are neutral on the stock market is 299 999 = 0 . 30 . c. The point estimate of subscribers who are bearish on the stock market is 291 999 = 0 . 29 . Problem 7.25 a. We first need to find the distribution of ¯ x . The distribution will be normal because we have a large sample size. The mean of ¯ x is 1020. The standard deviation of ¯ x is 100 √ 75 = 11 . 5. So the probability that ¯ x is within 10 of the population mean is the probability that ¯ x is between 1010 and 1030. So we haveis between 1010 and 1030....
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This note was uploaded on 01/24/2011 for the course STATISTICS 19897 taught by Professor Jager,abigaill during the Spring '10 term at Kansas State University.
 Spring '10
 Jager,AbigailL
 Standard Deviation

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