calculate the probability of tossing a coin 15 times and getting the given number of heads. round the answer to 4 places.

Question

anonymous · Answer

please advise what does that mean.

amistre64 · Answer

what is the given number of heads?

amistre64 · Answer

the answer is the binomial im sure

anonymous · Answer

the number of heads are 4, 7 and 10

amistre64 · Answer

15 C #heads * .5 right?

amistre64 · Answer

15.14.13.12
----------- * 1/2
    4.3.2

15.14.13.12.11.10.9
------------------- * 1/2
    7.6.5.4.3.2


15.14.13.12.11
--------------- * 1/2
    5.4.3.2

anonymous · Answer

are you doing factorial? please advise

amistre64 · Answer

i am..

15 P 4
------ * 1/2
    4!


15 P 7
------ * 1/2
   7!


15 P 5
------ * 1/2
    5!

zarkon · Answer

$$_{15}C_{n}(.5)^{15}$$

where n is the number of heads

amistre64 · Answer

i dont think its .5^(15) tho.  that looks odd to me

amistre64 · Answer

or is it nCr.p.q?

amistre64 · Answer

I aint got me ti83 handy to check :)

zarkon · Answer

$$P(X=x)=_{n}C_{x}p^x(1-p)^{n-x}$$

follows the binomial distribution

anonymous · Answer

i have a ti83 to check....how do you put that information in?

amistre64 · Answer

2nd, vars, binomialpdf(15,.5), sto, 2nd, 2

then fill in list 1 with 0,1,2,3,4,5, ... , 14,15

then stats, calc, 1-vars, L1,L2

amistre64 · Answer

that last step is prolly off ... 

L1 tells you the number of head; and the binomial of L2 gives the probability

amistre64 · Answer

1-variables stat is usually to get the mean and sd and such ...

zarkon · Answer

Let n=15 and x= # of heads

$$P(X=x)=_{n}C_{x}p^x(1-p)^{n-x}$$
$$=_{15}C_{x}(.5)^x(1-.5)^{15-x}$$
$$=_{15}C_{x}(.5)^x(.5)^{15-x}$$
$$=_{15}C_{x}(.5)^{x+15-x}$$
$$=_{15}C_{x}(.5)^{15}$$

anonymous · Answer

when do press enter?

zarkon · Answer

$$_{15}C_{x}=\frac{15!}{x!(15-x)!}$$

amistre64 · Answer

that way is good too :)

binomialpdf(15,.5,#heads) is the direct answer without the list

amistre64 · Answer

binomialpdf(15,.5,4), enter for 4 heads

binomialpdf(15,.5,7), enter for 7 heads

binomialpdf(15,.5,10), enter for 10 heads

zarkon · Answer

http://www.wolframalpha.com/input/?i=binomialpdf%2815%2C.5%2C4%29

amistre64 · Answer

2nd, enter gets you back to what you did prior without having to go thru the distr menu again

anonymous · Answer

good answers to you both