Question 209316
Suppose there are 10 items on a true-false quiz. The person taking the test does not read the questions; he just answers the questions randomly. What is the probability of his guessing all answers correctly?
How should I find out how many answers he answered correctly?? 


Since we're trying to find out a specific number of successes, 10, based on the probability of success, and probability of failure, we just use the binomial probability formula, which states:


P(s successes in n trials) = {{{_[n]C[s]*p^s*q^(n-s)}}}, where:

n = number of trials ; s = number of successes ; p = probability of success, and q = probability of failure


Applying the formula, we get: {{{_[10]C[10]*.5^10*q^(10-10)}}}


=  {{{1 * .5^10 * 1}}}  =  {{{highlight_green(0.000977)}}}