样本含量分别为n[img=~/QImg/2013-10-14-10-49-09/image019.jpg]和n[img=~/QImg/2013-10-14-10-49-09/image025.jpg]的两样本率分别为P[img=~/QImg/2013-10-14-10-49-09/image019.jpg]和P[img=~/QImg/2013-10-14-10-49-09/image025.jpg],则其合并平均率P[img=~/QImg/2013-10-14-10-49-09/image033.jpg]

A、P[img=~/QImg/2013-10-14-10-49-09/image019.jpg]+P[img=~/QImg/2013-10-14-10-49-09/image025.jpg]
B、P[img=~/QImg/2013-10-14-10-49-09/image019.jpg]+P[img=~/QImg/2013-10-14-10-49-09/image025.jpg])/2
C、p[img=~/QImg/2013-10-14-10-49-09/image019.jpg]xP[img=~/QImg/2013-10-14-10-49-09/image025.jpg]
D、n[img=~/QImg/2013-10-14-10-49-09/image019.jpg]P[img=~/QImg/2013-10-14-10-49-09/image019.jpg]+n[img=~/QImg/2013-10-14-10-49-09/image025.jpg]P[img=~/QImg/2013-10-14-10-49-09/image025.jpg])/(n[img=~/QImg/2013-10-14-10-49-09/image019.jpg]+n[img=~/QImg/2013-10-14-10-49-09/image019.jpg])
E、n[img=~/QImg/2013-10-14-10-49-09/image019.jpg]-1)P[img=~/QImg/2013-10-14-10-49-09/image019.jpg]+(n[img=~/QImg/2013-10-14-10-49-09/image025.jpg]-1)P[img=~/QImg/2013-10-14-10-49-09/image025.jpg]/(n[img=~/QImg/2013-10-14-10-49-09/image019.jpg]+n[img=~/QImg/2013-10-14-10-49-09/image025.jpg]-2)