SOLUTION: Thirty percent of students at a large university are known to be short-sighted. If twenty Students are picked at random, find the probability that at most two of them are shortsi

Algebra ->  Probability-and-statistics -> SOLUTION: Thirty percent of students at a large university are known to be short-sighted. If twenty Students are picked at random, find the probability that at most two of them are shortsi      Log On


   



Question 1150212: Thirty percent of students at a large university are known to be short-sighted. If twenty
Students are picked at random, find the probability that at most two of them are shortsighted.

Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
binomial with n=30 and p=0.3
probability 0 are short sighted is 0.7^30
probability 1 is short sighted is 30*0.7^29*0.3, The 30 being the number of different ways
probability of 2 is 30C2*0.7^28*0.3^2
first is 0.00002
second is 0.0003
third is 0.0018
the probability is 0.0021. Table shows the same.
expected value is 6
variance is 4.2 sd is 2.05