Question 168719
A student takes a 20-question, multiple-choice quiz with 5 choices for each question, find the probability of guessing at least 15 correct out of the 20. Would you consider this event likely or unlikely to occur?
<pre><font size = 4 color = "indigo"><b>
On your TI-83 or TI-84 calculator, type in

1-binomcdf(20,1/5,14)

and press ENTER.

You'll see {{{1.802764E-7}}} which means

{{{matrix(1,3,1.802764, "×", 10^(-7))}}}

or {{{0.0000001802764}}}

which is about 1 chance in 5.5 million.

So it's extremely unlikely.

Edwin</pre>