Posted by nathalie on .
suppose 25% of the urban population is 18 years old or younger. five residents of that city are selected at random find the probability that at least two of the selected five persons are 18 years old or younger. please help me with this question !!!

statistics 
MathGuru,
Here's one way to do this problem:
n = 5
p = .25
q = 1  p = 1  .25 = .75
You can do this: you can find P(0) and P(1), add both values together, then subtract from 1.
You can use a binomial probability table, or calculate by hand using the following formula:
P(x) = (nCx)(p^x)[q^(nx)]
I hope this will help.