Question 1178697
For each question, the probability of answering correctly is 0.5, and the 
questions are independent of each other. This situation is described by
a binomial probability distribution. The mean of a binomial distribution
is mu = n*p, where p is the probability of a success and n is the number of 
trials. Thus mu = 0.5*30 = 15.
The standard deviation is given by sqrt(np(1-p) = sqrt(30/4) = 2.739