"Passing" would entail getting 6 or more answers correct.
One way in which to calculate this probability would be to use the
"binomcdf(" function available on TI calculators.
binomcdf(10,0.2,0) produces a list of cumulative binomial probabilities for n=0 to n=10. We take the 6th such sum; it is 0.9936. This is the probability that the student, choosing answers at random, will get 5 or fewer answers right. (In other words, it's awfully hard to guess your way thru a multiple-choice test.)
Subtracting 0.9936 from 1.0000 produces the probability 0.0064 This is the probability of getting 6 or more questions right by guessing.
