Question

Probability- In a certain population, 7% of the people have Rh-positive blood. In a sample of 6 people from this population a) What is the probability that none have Rh-positive blood? b) What is the probability that 5 or less people have Rh-positive?

Answer 1

This is a binomial distribution

Explanation:

A binomial distribution has the expresion
`P(x=k)=nCk·p^k·q^(n-k)` where `q=1-p` and `nCk=(n!)/(k!(n-k)!)` and n is the sample size

In our problem `p=0.07`, then `q=1-0.07=0.93` and `n=6`

Let be `x`=number of people with RH+

We need to calculate `P(x=0)=6C0p^0q^(6-0)=1·1·0.98^6=0.78`

Now they are asking `P(x<=5)=P(x=6)=6C6p^6q^0=1.17xx10^(-7)=0.000000117`