Question

there are 5 questions of a test; each question has 6 choices, of which only 1 is correct.

What is the probability of guessing 2 wrongs and 3 correct?

Answer 1

\[\dbinom{5}{2}(\frac{1}{6})^3\times (\frac{5}{6})^2\]

Answer 2

good afternoon guru. you wanna number for this or just testing?

Answer 3

well, im trying to verify my answer to the study guide:)

I got 25/7776 for it :)

Answer 4

how many possible combinations of 2w and 3c are there? that one i get stuck on

Answer 5

there are
\[\dbinom{5}{2}\] of them

Answer 6

forget choosing 2 and 3. just choose 2 because if you have two you also have the other three. like tossing a coin 5 times and asking how many ways to get 2 heads. same as saying "how many ways to get 2 heads and 3 tails"

Answer 7

only two possibilities. "bernoulli trials" is the term of art and the formula is
\[P(X=k)=\dbinom{n}{k} p^k(1-p)^{n-k}\]

Answer 8

that looks like the binomial probability distribution :)

Answer 9

where \[P(X=k)\] means the probability you get exactly k successes in n trials. yes binomial is exactly what you have

Answer 10

;)

Answer 11

they don't call me master for nothing!

Answer 12

lol .... how much do they charge you :)

Answer 13

plenty and that is just an estimate!

Answer 14

thanx :) Massa'

Answer 15

i got
\[\frac{125}{2592}\]

Answer 16

the answer finally emerged later in the day;

the first part(a) asked for the probablity of gett 2wrongs and 2 corrects:

1.1.1.5.5 25
-------- = -----
6^5 7776

the part(b) saisd; how many ways is there to get 2wrong and 3 correct; I kept coming up with 10 and had no clue what to do with it :)

cccww ccwcw cwccw wcccw
ccwwc cwcwc wccwc
cwwcc wcwcc
wwccc................................ 10 ways to do it.

part(c) what is the probability of getting 2wrong and 3 correct;

25 250
----- * 10 = ----- ; reduces as wanted
7776 7776

:) thanx

Answer 17

two wrong and 2 correct? what is the 5th? now answer?

Answer 18

2wrong and 2 correct out of 5 questions? I dont quite understand the question :)