Sampling distribution

# Sampling distribution - STAT 1220-090 HOMEWORK 4 Name Fall...

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STAT 1220-090 HOMEWORK 4 Fall 2011 Name: ____________ Score_________ 1. Given that the population mean μ = 68 and population standard deviation σ = 12, find the sample mean μX and the sample standard deviation σX for a random sample of size 50 (round off to two decimal places.) (a) 68, 12 (b) 9.62, 12 (c) 9.62, 1.70 (d) 68, 1.70 (e) 68, .24 For questions 2 and 3. It is known that the mean diameter of pine trees in a national forest is 9.6 (inches) with a standard deviation 2.4 (inches). Assuming that the tree diameters are distributed normally. 2. If a pine tree is to be selected randomly from this forest, what is the probability that its diameter will fall between 7.2 inches and 14.4 inches? (a) .1359 (b) .6826 (c) .9544 (d) .8185 (e) .9772 3. If a selected pine tree from this forest is at the 90th percentile, what is its diameter (rounded off to two decimal places) in inches? (a) 12.67 (b) 14.30 (c) 13.55 (d) 14.69 (e) 18.19 4. Personal best finishing times for a particular race in high school track meets are normally distributed with mean 5.27 minutes and standard deviation .42 minutes. If the qualifying time for this event for the regional championship is to be set so that only four percent of all runners

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Sampling distribution - STAT 1220-090 HOMEWORK 4 Name Fall...

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