1) The life of a model of a wristwatch cell is 22 months with a standard deviation of 4 months and is approximately normally distributed. How many months should the manufacturer warantee the cell so that not more than 15% of the cells will fail before the warranty expires?
2) Let X be an exponentially distributed random variable such that P( X > 1) = 0.367879. Find E(X).
3) A random variable X has gamma distribution with parameters alpha = 2 and beta = 3. Find P(x > 9).
4) The variable X is normally distributed.The mean is ? = 22.0 and the standard deviation is ? = 2.4.
Find P(19.7 < X < 25.3).
5) Find the z-score for having area 0.09 to its right under the standard normal curve, that is, find z0.09
6) The area that lies between 0 and 3.01