Question

MEDAL!!


A researcher wants to conduct a genetic study using 15 randomly-selected volunteers. He has a volunteer pool of 30, composed of 15 males and 15 females. What is the probability that the randomly-selected group will be all male OR all female?
A. 1/155,117,520
B. 1/77,558,760
C. 1/310,235,040
D. 1/450

Answer 1

D right?

Answer 2

this one is a little trickier

Answer 3

you know what 15! stands for?

Answer 4

yes rendomly selected volunteers

Answer 5

actually i mean what does a number with an exclamation mark behind it mean?

Answer 6

i dont know lol whatever u want it to mean

Answer 7

lol, no it's actually a mathematical symbol used for statistics/probability.

Answer 8

never knew that lol

Answer 9

i hope you have a calculator with a ! button on it.

Answer 10

the last two questions we did, we had things like (45/15)*(45/14) etc right?

Answer 11

i do and yea

Answer 12

cool, the ! does exactly that.

Answer 13

so instead of typing 15*14*13*12*11*10*9*8*7*6*5*4*3*2*1 you can simply type 1`5! and it means the same.

Answer 14

i mean 15! i accidentally hit the `key

Answer 15

numbers with ! are really large once you get past like 10! or so. in fact, most calculators can't even calculate numbers bigger than 69!

Answer 16

okay and i get this:

1,307,674,368,000

Answer 17

when i type in 15!

Answer 18

correct, that's not the answer to the problem, but that's how much 15! is

Answer 19

now, if you do for example \(\Large \frac{ 15! }{ 10! } \) you will end up with 15*14*13*12*11

Answer 20

note that the 10! which you will divide by will cancel out everything below the 10

Answer 21

we are going to use that to calculate our probability in this problem.

Answer 22

\[\large \frac{ 15! }{ 30!/15! }*2\] try this

Answer 23

btw, if your calculator has a ! button it may also have a nCr button.

Answer 24

im using an online calculator, cause besides that all i have is my phone and its being really slow.

Answer 25

ya its not loading :/

Answer 26

ok, 30nCr15 means the same as \(\large \frac{ 30! }{ 15!*(30-15)! }\) in case you want an even shorter notation

Answer 27

http://www.wolframalpha.com/ try using that as calculator lol

Answer 28

http://www.wolframalpha.com/input/?i=2%2F%2830+ncr+15%29

Answer 29

i got 265

Answer 30

calculator didn't interpret it right probably, try wolfram, or use brackets.

Answer 31

2*15!/(30!/15!) should work

Answer 32

okay i got it lol, i got 155, 117520

Answer 33

so A is the answer than

Answer 34

really?
what did you write?

Answer 35

hmm, that's exactly half of the answer so you probably missed the *2

Answer 36

note that you can either have all male or all female, so that's why the *2

Answer 37

(30!)/(15!*(30-15)!

Answer 38

that's the number of possible combinations

Answer 39

divide two by that number and you have the probability you need. 2/((30!)/(15!*(30-15)!))

Answer 40

but really, why did your teacher give you probability homework without even explaining all this?