Question

According to a government commision, 70% of all the nation’s households have vcrs. In a random sample of 15 households, what is the probability that exactly 10 have vcrs

Answer 1

Answer: P(10,15,0.7)=3003*0.7^10*0.3^5=approx 0.2061

Explanation:

The required probability P(10,15,0.7)= C15 10 *p^10*q^(15-10) where

C15 10= 15 !/10!/5!= 11*12*13*14*15/(2*3*4*5)=11*12*13*14/(2*4)=11*3*13*7=

=77*39=3003

p=0.7 q=1-p =1-0.7= 0.3 (probability of not having vcrs)

So P(10,15,0.7)=3003*0.7^10*0.3^5=approx 0.2061