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Exercises
1. Assume that the average annual family income in a given city is $28,000 with standard
deviation $3200. If a random sample of fifty families is taken, what is the chance that the
average income of the fifty families will be over $29,000?
2. Assume that 2% of all light bulbs produced at a factory are defective. If
a random sample of 150 bulbs is taken, what is the probability that less
than 4% of the sample bulbs are defective?
Solutions
1. normalcdf(29000, 1E99, 28000, 3200/ 50 ) = .013 = 1.3%.
2. normalcdf(−1E99, 0.04, .02,
150/98.*02. ) = .96 or 96%.
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