Q8 of 99 Page 33

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.

Let p = probability of selecting defective bolt, so


p = 0.1



q = 1 – p




Given, n = 400,


(i) mean = np




(ii) Standard deviation =


=


=


∴ Standard deviation = 6


So, mean = 40, standard deviation = 6


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