Q10 of 99 Page 33

If on an average 9 ships out of 10 arrive safely to ports, find the mean and S.D. of ships returning safely out of a total of 500 ships.

Let p be the probability of a ship returning safely to ports, so





Given, n = 500


Mean = np


=


= 450


∴ Mean = 450


Standard deviation =




= 6.71


So, mean = 450, standard deviation = 6.71


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