1.

A bag contains 30 white balls and 10 red balls. 16 balls are drawn one by one randomly from the bag with replacement. If X be the number of white balls drawn, then (mean of X/standard deviation of X)  is equal to :(1)   4√3(2)  4√3/3(3)  4(4)   3√2

Answer»

Correct option  (1)   4√3

Explanation:

Probability of getting a white ball = 30/40 = 3/4

Probability of getting a red ball =10/40 = 1/4

n = 16

Mean = np and variance = npq

So mean = 16.3/4 and s.d. = √16.3/4.1/4

So mean = 12 and s.d. = √3

so mean of x/s.d of x = 12/√3 = 4 x 3/√3 = 4√3



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