A manufacture of floor wax has developed two new brands, A and B, which sge wishes to subject to homeowners' evaluation to determine which of the two is superior. Both waxes, A and B, are applied to floor surfaces in each of 15 homes. Assume that there is actually no difference in the quality of the brands. What is the probability that ten or more homeowners would state a perference for
a. brand A? ans: 0.151 b. either brand A or brand B? ans: 0.302
Of the volunteers donating blood in a clinic, 80% have the Rh factor present in their blood. What is the smallest number of volunteers who must be selected if we want to be at least 90% certain that we obtain at least 5 donors with Rh factor?
95354008@(季圓-統計學輔導員 ) 2008-10-22 16:09:04
第一題題目中有提到Assume that there is actually no difference in the quality of the brands，所以是用1/2代。而代入1/2後可以binomial機率分配公式求得喜歡brand A的機率，即binomial分配 n=15 求P(X>=10)的機率，答案是進位後是0.151沒錯。