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Normal Density

# Normal Density - 65 mph b What percentage of cars go above...

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Statistics 113 Fall 2010 Normal Density (Part 1) 1) The distribution of heights of American women aged 18 to 24 is approximately normally distributed with mean 65.5 inches and standard deviation 2.5 inches. Using the 68-95- 99.7 Rule answer the following questions: a) Of these American women what percentage have heights between 63 and 68 68% American women have heights between 63 and 68. b) Of these American women 95 % of them fall in what height range? 95% of these American women fall between the range of 60.5 and 70.5. 2) A sample of the cars traveling along the Tri-City Highway approximates a symmetrical, bell-shaped distribution. Suppose the mean (or average) speed is 60 mph with a standard deviation (σ) of 5 mph. a) What is the speed of 68% of the cars?

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Unformatted text preview: 65 mph b) What percentage of cars go above 70 mph 2.5% c) What percentage of cars travel between 55- 75 mph? 83.85% 3) Scores on the IQ test for the 20 to 34 age group are approximately normally distributed with mu= 100 and standard deviation= 30. Use the 68-95-99.7 rule to answer these questions. a) About what percent of people in this age group have scores above 100? 50% b) About what percent have scores above 160? 2.5% c) In what range do the middle 95% of all IQ scores lie? 40-160 d) Approximately what percentage would score above 70 84% e) Approximately what percentage of this group score between 40 and 100 47.5% f) Approximately what percentage of this group score below 70 16%...
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