Binomial

S

Sue20

New member
Joined
Oct 5, 2011
Messages
20
Flip a fair coin 4 times. What is the probability of observong exactly three heads?
* Should I use binomialpdf or use the HHH method? Please Help!!
 
I would use the binomial distribution formula. You want 3 heads each head with a probability of 0.5 of occurring....take it from here...
 
Sue20 said:
Flip a fair coin 4 times. What is the probability of observong exactly three heads?
Click to expand...
How many ways are there to arrange this string \(\displaystyle hhth~?\)
Then multiply that by \(\displaystyle (0.5)^4~.\)
 
There are 4 ways so would you mulitply (0.5) (0.5) (0.5) (0.5)?
 
Sue20 said:
There are 4 ways so would you mulitply (0.5) (0.5) (0.5) (0.5)?
Click to expand...
You have missed to whole point!
There are four ways to arrange \(\displaystyle THHH\) and each arrangement has probability \(\displaystyle (0.5)^4\).
So what is the answer?
 
Sue20 said:
Is it .25? .0625 x 4= .25
Click to expand...
Correct.
If you toss a coin ten times the probability of exactly seven heads is
\(\displaystyle \dbinom{10}{7}(0.5)^{10}=\dfrac{10!}{7!\cdot 3!}(0.5)^{10}\)

If you toss a coin N times the probability of exactly \(\displaystyle 0\le K \le N\) heads is
\(\displaystyle \dbinom{N}{K}(0.5)^{N}=\dfrac{N!}{K!\cdot (N-K)!}(0.5)^{N}\)
 
You must log in or register to reply here.
Top