Posted by **Ben** on Wednesday, May 23, 2012 at 3:08pm.

Claire takes a five-question true-false test. She hasn't studied, so she guesses at random. With her ESP she figures she has a 60% probability of getting any one answer wrong.

A. What is the probability of getting an answer wrong? (Do you think they want me to ignore the ESP nugget or take it into account?)

b. Let P(x) be the probability of getting exactly x of the five answers right. Calculate p(0) through P(5)

c. What is the probability of getting at least three answers right.

- Math/Prob -
**MathMate**, Wednesday, May 23, 2012 at 3:27pm
We will have to assume the ESP estimation is correct.

The resulting distribution is binomial, with 5 questions, and probability of success p=1-0.6=0.4, q=1-p=0.6 (failure).

The probability of getting exactly n question correct (out of 5) is given by the binomial coefficient

C(5,n)p^n q^(5-n)

where C(5,n)=5!/(n!(5-n)!)

Example:

probability of getting 3 answers right

=P(3) = [5!/(3!2!)]0.4^3 0.6^2

=0.2304

To calculate the probability of getting at least three correct would be:

P(3)+P(4)+P(5)=0.317

## Answer This Question

## Related Questions

- Statistics - Please help. Find the probability of getting 2 hearts if the cards ...
- Statistics Algebra 2 - A 10-question multiple choice test has 4 possible ...
- statistics - A multiple choice test has 20 questions with each having 4 possible...
- Statistics - A multiple choice test has five choices. Therefore the probability ...
- Math - On a true-false test, each question has exactly one correct answer: true...
- PROBABILITY MATH - An unprepared student makes random guesses for the ten true-...
- math - A true-false test consists of 15 items. (a) If Chris does not study at ...
- stats again - ok I get it, so once I get the prob figred for one person, how do ...
- MATH Prob. - Jack is taking a four-item trueâ€“false test. He has no knowledge ...
- Math - A student takes a true-false test exam with 10 questions. If the student ...

More Related Questions