posted by Sue on .
A multiple choice test has five choices. Therefore the probability of getting the correct answer by guessing is 0.2. The test has six questions. Use the binomial formula with n = 6 and p = 0.2 to (a) Determine probability of getting two questions correct.
(b)Determine probability of getting between one and four (inclusive) correct
If the events are independent, the probability of both/all events occurring is determined by multiplying the probabilities of the individual events.
2 correct = .2^2 * .8^4 = ?
1 correct = .2 * .8^5 = ?
3 correct = .2^3 * .8^3 = ?
4 correct = .2^4 * .8^2 = ?
Either-or probabilities are found by adding the individual probabilities, so add the probabilities you have found.
A unbiased die is thrown seven times. Find the probability of throwing at least five six's.