A die is rolled 20 times . Getting a number greater than 4 is a success.
Find the mean and variance of the number of successes .

Explanation

In a single throw of a die , we have
p= probability of getting a number greater than `4 =(2)/(6)=(1)/(3)`
`:. Q =(1- p) =(1-(1)/(2)) =(2)/(3)`
Also n=20 (given)
`:. ` mean =np = `(20 xx (1)/(3)) =6.67 ` and
variance =npq `=(20 xx (1)/(3) xx (2)/(3)) =4.44`