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q5s - 2 points Solution True 2 SEs = 0.14(d 95 of the...

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Math 127B, Quiz 5 Thursday, February 24th, 2011 Name: Recitation Section: Ten minutes. Calculators allowed. 20 points maximum. 1. A survey organization takes a simple random sample of 625 houesholds from a city of 80,000 households. On the average, there are 2.3 persons per sample household, and the SD is 1.75. Say whether each of the following statements is true of false, and explain. (a) The SE for the sample average is 0.07. [ 10 points] Solution True. The SE for the sum is 625 × 1 . 75 = 25 × 1 . 75 = 43 . 75. The SE for the average of the draws is 43 . 75 / 625 = 0 . 07. (b) A 95%-confidence interval for the average household size in the sample is 2.16 to 2.44. [ 2 points] Solution False. The confidence interval is for the parameter. (c) A 95%-confidence interval for the average household size in the city is 2.16 to 2.44. [
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Unformatted text preview: 2 points] Solution True. 2 SEs = 0.14. (d) 95% of the households in the city contain between 2.16 and 2.44 persons. [ 2 points] Solution False. Makes no sense there is no whole number between 2.16 and 2.44! (e) The 95% conﬁdence interval is about right because household size follows the normal curve. [ 2 points] Solution False. The histogram may not be normal. in fact it’s not, since 2 . 3-2 × 1 . 75 is negative. (f) The 95% conﬁdence level is about right because, with 625 draws from the box, the probability histogram fo the average of the draws follows the normal curve. [ 2 points] Solution True. The average of draws follows a normal curve. 1...
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