Q13 of 99 Page 33

Find the expected number of boys in a family with 8 children, assuming the sex distribution to be equally probable.

Let n and p be the parameters of the binomial distribution.


Let, p = probability of having a boy in the family


Given, p = q


Since, p + q = 1


⇒ p + p = 1


⇒ 2p = 1




Given, n = 8


The expected number of boys = np



= 4


The expected number of boys = 4


More from this chapter

All 99 →
11

The mean and variance of binomial variate with parameters n and p are 16 and 8 respectively. Find P (X = 0), P (X = 1) and P (X ≥ 2).

 12

In eight throws of a die 5 or 6 is considered a success, find the mean number of successes and the standard deviation.

 14

The probability is 0.02 that an item produced by a factory is defective. A shipment of 10,000 items is sent to its warehouse. Find the expected number of defective items and the standard deviation.

 15

A die is thrown thrice. A success is 1 or 6 in a throw. Find the mean and variance of the number of successes.