Tuesday, July 28, 2009

Math question?

A multiple choice test consists of 25 questions with possible answers of a, b, c, d, and e. Estimate the probability that with random guessing, the number of correct answers is between 3 and 10 inclusive.

Math question?
For this problem, use the Binomial Probability Formula:





P(N) = N! / [k! * (N - k)!] * p^k * q^(N - k)





where:


N = Number of opportunities for event x to occur (25)


k = Number of times that event x should happen (3)


p = Probability of a success (.2)


q = Probability of failure (.8)


! = Factorial





Let's compute the probability of getting 3 correct answers:


P(k) = N! / [k! * (N - k)!] * p^k * q^(N - k)


P(3) = 25! / [3! * (25 - 3)!] * (.2)^3 * (.8)^(25 - 3)


P(3) = 0.135768 or 13.58%





Do this for P(4), P(5), P(6), P(7), P(8), P(9) and P(10).


Add them up:


P(3) = 0.135768


P(4) = 0.186681


P(5) = 0.196015


P(6) = 0.163346


P(7) = 0.110842


P(8) = 0.062349


P(9) = 0.029442


P(10) = 0.011777


P(3 ≤ x ≥ 10) = 0.8962 or 89.62%





Exact Answer:


0.89621985666883783 ← correct to 17 decimal places.





Yeah, the math gets really messy,


but you can use an online Binomial Probability Calculator:


http://faculty.vassar.edu/lowry/ch5apx.h...





Or you can do it on your TI-83/84 Calculator:


http://mathbits.com/MathBits/TISection/S...





Good luck in your studies,


~ Mitch ~





P.S - I hope my explanation is clear, if not,


you're are welcome to e-mail me with any questions.
Reply:Glad to help... and thanks for the stars!


~ Mitch ~ Report It

Reply:c


my teacher said if your testing and absaloutly have no clue best stay with c


in monst tests inwas the most chosen correctly


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