Statistics  math
posted by Gina .
Each consumer has a 25% chance of preferring your product over the competitor's product. If we question 15 customers, what is the probability that at least 3 will prefer your product?

1(3/4)^15C(15,1)(1/4)(3/4)^14 C(15,2)(1/4)^2(3/4)^13

Do you have an answer that I can check my calculations with? I haven't worked a problem like this in a long time  am trying to help a friend with this problem. We're having trouble calculating it. I'm using a regular calculator, not a scientific one. Any suggestions