All GRE Subject Test: Math Resources
Example Question #1 : Binomial Distribution
A fair coin is tossed 15 times. What is the probability of observing less than 3 heads?
This problem uses the Binomial Distribution:
For this problem n is the number of trials, or 15. Because the problem stated that the coin was a fair coin the probability of heads is one half, or .5.
The binomial distribution is a discrete distribution so the expression x<3 has to be broken down.
Adding the probabilities will give the final answer.