The manufacturing time, X, for an item produced by a machine has distribution function F(t) = 1 − e−2t2

, t ≥ 0.

Then, the probability P(X > 2) equals e−8.

16. A random variable has probability density f (x) = x3∕4, 0 ≤ x ≤ 2.

The variance of X is 8∕75.