Question

3. (5 pts.) Rh-positive blood appears in 85% of the white population in the United States. If 10 people are sampled at random from that population, find the probability that

(a) eight of them have Rh-positive blood.

(b) at least 8 of them have Rh-positive blood.

Please show work will rate!!!

Answer 1

We have here, n = 10 , p = 0.85

We can use here binomial probability distribution.

(a) the probability that eight of them have Rh-positive blood.

P[x=8]= C(10, 8)*(0.85)^8*(1-0.85)^2

=0.2759

(b) the probability that at least 8 of them have Rh-positive blood.

=0.2759 + 0.3474 + 0.1969

=0.8202

Since,

P[X=8] = C(10, 8)(0.85)^8(1-0.85)^2 = 0.2759

P[X=9] =C(10, 9)(0.85)^9(1-0.85)^1 = 0.3474

P[X=10]=C(10, 10)(0.85)^10(1-0.85)^0 = 0.1969

Alternatively, by using Excel command.

a) P[X=8] = BINOMDIST(8,10,0.85,FALSE) = 0.2759

b)

  

  =1-BINOMDIST(7,10,0.85,TRUE)

=0.8202