SOLUTION: Suppose a student takes a multiple choice test with 10 questions and he randomly guesses the answers (say he forgot to study). Each questions has five choices but only one right an

Click here to see ALL problems on Probability-and-statistics

Question 450023: Suppose a student takes a multiple choice test with 10 questions and he randomly guesses the answers (say he forgot to study). Each questions has five choices but only one right answer. What is the probability that he gets at least 7 right out of the 10 questions.
I am unsure how to work this problem.

Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website!
Suppose a student takes a multiple choice test with 10 questions and he randomly guesses the answers (say he forgot to study). Each questions has five choices but only one right answer. What is the probability that he gets at least 7 right out of the 10 questions.
---
Binomial Problem with n = 10 and p = 1/5
---
P(5<= x <=10) = 1-P(0<= x <=4) = 1-binomcdf(10,1/2,4) = 0.6230
==================
I used a TI-84 to get the numbers.
==================
Cheers,
Stan H.
==========