Q1. The average thickness of books on a library shelf is 8.3 centimeters. The standard deviation is 0.6 centimeter. If 20% of the books are oversized, find the minimum thickness of the oversized books on the library shelf. Assume the variable is normally distributed. Ans Value of z to the cumulative probability above of 0.20 from normal table is 0.84 P( x-u/ (s.d/sqrt(n) ) > x - 8.3/ (0.6/sqrt(1) ) = 0.8 That is, ( x - 8.3/ (0.6/sqrt(1) ) = 0.84 --> x = 0.84 * 0.6/sqrt(1) + 8.3 = 8.804 Q2. The average repair cost of a microwave oven is $55, with a standard deviation of $8. The costs ar ...
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