SOLUTION: If the probability of defective bolt be 1/10,Find the mean and variance for binomial distribution of defective bolts in a sample of 400 bolts.

mean = (number)×(probability)

mean = 400× = 40

variance = (number)×(probability)×(One minus probability)

variance = (400)×(1/10)×(1-) = (400)×()×(-) = (400)×()×() = 40× =  = 36

Edwin