- #1
Bassalisk
- 947
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Homework Statement
Say we do 4 coin flips. If the order matters, of which coins come up, total number of possibilities are 2*2*2*2=24 (i imagine this like getting 16 different binary numbers)
Did I got this right?
Now If we want to find the probability to get a combination with 2 heads and 2 tails(not with that order, just a combination that has 2 heads and 2 tails).
[itex]P(2,2)={\Large \frac{4!}{2!\cdot 2!\cdot 2^{4}}}[/itex]
1 H H H H
2 T H H H
3 H T H H
4 H H T H
5 H H H T
6 T T H H
7 H T T H
8 H H T T
9 T H H T
10 T H T H
11 H T H T
12 T T T H
13 T T H T
14 T H T T
15 H T T T
16 T T T T
This is analogues to getting a binary number that has exactly 2 zeroes and 2 ones, right?
Now for the second part:
Order DOESN'T matter. Say we toss a coin 4 times again. Total number of possibilities are:
H H H H
H T T T
H H T T
H H H T
T T T T
So getting precisely 2 heads and 2 tails, is 1/5, right?
But how do i calculate the possibilities when order doesn't matter? Other than writing all the possibilities by hand and counting them?