The Rh Factor In a certain population, 15% of the people have Rh-negative blood. A blood bank serving this population receives 92 blood donors on a particular day. What is the probability that 15 to 20 (inclusive) of the donors are Rh-negative? Use the continuity correction for this problem!!! Solution Given n=92, p=0.15 mean=n*p=92*0.15=13.8 standard deviation=sqrt(n*p*(1-p))=sqrt(92*0.15*0.85)= 3.424909 So the probability is P(15 <=X<= 20)= P(14.5.