# 10_13ans - STAT 400 . Examples for 10/13/2011 Fall 2011 The...

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STAT 400 Examples for 10/13/2011 Fall 2011 ½ . The true weight of “10-pound” sacks of potatoes processed at a certain packaging house follows a normal distribution with mean of 10.1 pounds and standard deviation of 0.2 pounds. a) What is the probability that a sack weighs at least 10 pounds? P ( X 10 ) = - 2 . 0 1 . 10 10 Z P = P ( Z 0.50 ) = 1 – Φ ( 0.50 ) = 1 – 0.3085 = 0.6915 . b) A random sample of 9 sacks is selected. What is the probability that the average weight of these 9 is at least 10 pounds? Case 2. Z X σ μ = - n . P ( X 10 ) = - 9 2 . 0 1 . 10 10 Z P = P ( Z 1.50 ) = 1 – Φ ( 1.50 ) = 1 – 0.0668 = 0.9332 .

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1. A student commission wants to know the mean amount of money spent by college students for textbooks in one semester. Suppose the population mean is \$450 and the population standard deviation is \$40. A random sample of 625 students is taken. a)
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## This note was uploaded on 11/07/2011 for the course STAT 400 taught by Professor Kim during the Fall '08 term at University of Illinois, Urbana Champaign.

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10_13ans - STAT 400 . Examples for 10/13/2011 Fall 2011 The...

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