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Unformatted text preview: least two years (730 days) without trouble? P( X ≥ 730 ) = ≥ 100 3 6 730 Z P = P( Z ≥ 1.00 ) = 1 – Φ ( 1.00 ) = 1 – 0.8413 = 0.1587 . c) (4) A cleaning service purchased (a random sample of) 8 vacuum cleaners. Find the probability that the average duration of troublefree operation of those 8 vacuum cleaners will be at least two years (730 days). μ = 630, σ = 100, n = 8. Need P( X ≥ 730 ) = ? Since the population we sample from is normal, . n Z X =σ μ P( X ≥ 730 ) = ≥ 8 100 30 6 30 7 Z P = P( Z ≥ 2.83 ) = 1 – Φ ( 2.83 ) = 1 – 0.9977 = 0.0023 ....
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This note was uploaded on 02/15/2012 for the course STAT 400 taught by Professor Kim during the Spring '08 term at University of Illinois, Urbana Champaign.
 Spring '08
 Kim
 Statistics, Probability

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