Question

assume there are 4 grey females, 4 grey males, 2 white females, and 3 white males. As in the book, the biologist selects two mice randomly.
(1) What is the probability of selecting two males given that both are grey?

(2) What is the probability of selecting 1 mouse of each gender given that both are grey?

Answer 1

please help!!!

Answer 2

there are 4 grey males and how many total?

Answer 3

oh damn i answered some other question
i should learn how to read, ignore that post

Answer 4

for (1) I believe it is 4/8*3/7

Answer 5

thats not right

Answer 6

or 4C2/8C2

Answer 7

like 4 choose 2 over 8 choose 2?

Answer 8

yep

Answer 9

thats not right

Answer 10

put \(A\) as the event both chosen are males, \(B\) as the event both chosen are grey, and then compute
\[P(A|B)=\frac{P(A\cap B)}{P(B)}\]

Answer 11

\[P(B)=\frac{8}{13}\times \frac{7}{12}=\frac{14}{39}\]

Answer 12

14/39 isn't right

Answer 13

yes, it is not right, we are not done
we still have to compute \(P(A\cap B)\)
\(A\cap B\) is the event both chosen are grey males, it is
\[\frac{4}{13}\times \frac{3}{12}\]

Answer 14

better known as
\[\frac{1}{13}\]

Answer 15

so your answer should be
\[\frac{P(A\cap B)}{P(B)}=\frac{\frac{1}{13}}{\frac{14}{39}}=\frac{1}{13}\times \frac{39}{14}=\frac{3}{14}\]

Answer 16

that's exactly the same as 4C2/8C2

Answer 17

that is right!! do u know how to do the second part?

Answer 18

@pizzapi that is probably a snappier way of doing it, yes

Answer 19

but he/she said it was wrong

Answer 20

maybe less intuitive, but definitely quicker

Answer 21

how do you do the second part

Answer 22

(4C1*4C1)/(8C2)

Answer 23

thanks!!

Answer 24

hold phone, that one might not be right

Answer 25

Assume that the box contains 11 balls: 4 red, 4 blue, and 3 yellow. As in the text, you draw one ball, note its color, and if it is yellow replace it. If it is not yellow you do not replace it. You then draw a second ball and note its color.
(1) What is the probability that the second ball drawn is yellow?

(2) What is the probability that the second ball drawn is red?

Answer 26

do you know how to do that?

Answer 27

yes but hold on a second

Answer 28

part 2 was right.. my homework tells you right off when you enter if correct

Answer 29

yes, it is right i had a brain freeze
last problem you posted is harder and we have to work through it step by step

Answer 30

ok

Answer 31

a nice tree diagram might help let me see if i can draw one, because it is hard for me to draw here