Question

how to solve on excel? i do not have minitab

4. The blood type O negative is called the "universal donor" type, because it is the only blood type that may safely be transfused into any person. Therefore, when someone needs a transfusion in an emergency and their blood type cannot be determined, they are given type O negative blood. For this reason, donors with this blood type are crucial to blood banks. Unfortunately, this blood type is fairly rare; according to the Red Cross, only 7% of U.S. residents have type O negative blood. Assume that a blood bank has recruited 20 independent donors. a. What is the probability that two or more of them have type O negative blood? b. What is the probability that fewer than four of them will have type O negative blood? c. Would it be unusual if none of the donors had type O negative blood? Explain. d. What is the mean number of donors who have type O negative blood? What is the variance of the number of donors who have type O negative blood? e. /2 2 99%

Answer 1

for excel, formulas are highlighted in bold:

a) P(2 or more have type O blood) =P(X>=2) =1-P(X<=1) =1-binomdist(1,20,0.07,true) =0.4131

b)P(X<4)=binomdist(3,20,0.07,true) =0.9529

c) P(X=0) =binomdist(0,20,0.07,false) =0.2342 , as this is greater than 0.05 ; therefore this is not unusual if none of the donor had type O negative blood

d)

mean =np=20*0.07 =1.4

e)variance =np(1-p) =20*0.07*(1-0.07)=1.302