Question 732051
Find the probability: A 10-question multiple choice test has 4 possible answers
for each question.  A student guesses on all ten answer.  What is the
probability that the student selects at least 6 correct answers?

A.) 0.995 B.) 0.020 C.)0.118 D.) 0.989
<pre>
There are two ways to do it. You can either interpret this as

1. One minus the probability that the student will guess 5 or fewer 
correct answers with a probability of a correct answer being {{{1/4}}}:

1 - binomcdf(10,1/4,5) on your TI-83 or 84

Answer 0.0197277069 

or

2.  The probability that the student will guess 4 or fewer wrong answers
with a probability of a wrong answer being {{{3/4}}}.

binomcdf(10,3/4,4)

Answer 0.0197277069

------------------------

Either way it rounds to 0.020, choice (B).

That means if the student guesses, the student only has 2 chances
out of 100, or 1 chance in 50, of passing with a D or better by guessing.

Edwin</pre>