Question

The probability of defective bolts in a workshop is 40%. Find the mean and variance of defective bolts out of 10 bolts.

Answer 1

Let X denote the number of defective bolts.

p = probability of defective bolts.
p = 40%
p = `40/100` = 0.4
q = 1 -p = 0.6
Here n = 10
E (X) = np
        = 10 x 0.4
        = 4

V(X) = npq
       = 4 x 0.6
       = 2.4