Question

A multiple-choice test consists of 9 questions. Each question has answer choices of a, b, c, d, and e, and only one of the choices is correct. If a student randomly guesses on each question, what is the probability that she gets fewer than 2 of them correct?

Carry your intermediate computations to at least four decimal places, and round your answer to at least two decimal places.

Answer 1

Ok, so with the choices of: a, b, c, d, and e,
We have a total of 5 solutions to choose from.

How many questions does she randomly choose on? That's important to know.

Answer 2

Because for each question she will have a 1/5 chance of randomly selecting the right answer.

This is 20%.

Answer 3

She randomly guesses on all 9 questions

Answer 4

So I know that probability states she will get 20% of the questions correct, but I don't know how to calculate the probability of her getting less than 2 questions correct?

Answer 5

For each question she has 20% likelyhood to get it right. Since there are 9 questions, she has 9 tries of 20% to get right answers. This is shown by multiplying 20% times 9.

20% as a decimal is 0.20,

So 0.20 x 9 = (Your answer)

Answer 6

I think that just tells me how many she will likely get correct.. I need the probability of her getting less than 2 answers correct.

Answer 7

Well she will get 1.8 (less than two) right, if she randomly guesses on all of the nine, so I would say, since this is less than two, that it is 100% likely she will get less than two right after randomly choosing at a 20% rate 9 times.

Does that make sense?

Answer 8

oh.. yes that does. thank you!

Answer 9

Awesome, np.