A fair coin tossed 8 times. Find the probability of getting exactly 3 Heads

Question

hartnn · Answer

how much is the probability of getting one head ?

anonymous · Answer

it doesnt say

hartnn · Answer

let that probability be p, 
exactly 3 heads means , exactly 3 heads and 5 tails.
so the probability of getting exactly 3 Heads will be 
p^3 (1-p)^5 = ?

hartnn · Answer

the probability of getting one head in one coin toss is ?

hartnn · Answer

it won't say, u need to know it

anonymous · Answer

it says to use a table given but its confusing to read

hartnn · Answer

which table ?

anonymous · Answer

its in my book its a binomial table

hartnn · Answer

does the question say u need to use that or you can do it without the table also ?

anonymous · Answer

it says i can use it for binomial distribution

hartnn · Answer

u still have to figure :the probability of getting one head in one coin toss is ?

hartnn · Answer

one coin toss can either produce a head or tail.
so there is equal probability of getting those which is ?

anonymous · Answer

.5?

hartnn · Answer

that is correct!
so p= 0.5
using binomial distribution u get your probability as 
p^3 (1-p)^5 = (0.5)^3 (1-0.5)^5 = ?

anonymous · Answer

what symbol is ^?

hartnn · Answer

$\huge  (0.5)^3 (1-0.5)^5=?$

hartnn · Answer

or if u have to use table:
you can go to a Binomial Distribution Table and find the solution, values for n=8 and p=0.5, read from the section the probability of 3 which is ?

anonymous · Answer

.12?

hartnn · Answer

u have options/choices ?

anonymous · Answer

well it doesnt say i have to use the table

anonymous · Answer

would my answer be correct?

hartnn · Answer

i don't have the table, just look up for  values for n=8 and p=0.5, read from the section the probability of 3, that would be your answer

anonymous · Answer

ok thanks, appreciate the help

hartnn · Answer

welcome :)

raden · Answer

but, the sum of ways we need look also, right @hartnn  ?  
so, the sum of way be equal 8!/(3!*5!) ?

hartnn · Answer

would that be like multiplying 8C5 , yes, i thought it before....but since cst had a table, i then resorted to using table only....

hartnn · Answer

8C5 *p^3 (1-p)^5  will give the same value mentioned in table

hartnn · Answer

which would be like 0.21875, if i calculated it properly....

raden · Answer

yea, like that i mean