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Question
If the probability of a defective bolt is 0.1, find the (i) mean and (ii) standard deviation for the distribution of bolts in a total of 400 bolts.
Solution
Total number of bolts (n) = 400 and p = prob of defective bolts = 0.1
(i) Mean = np = 400(0.1) =40
(ii) Variance = npq = 40(1-0.1) = 36
So, the standard deviation =\[\sqrt{36} = 6\]
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