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# Probability Question Watch

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1. Hey there, I am stuck on the following question, can you help me out please?
Cheers

Suppose a football player scores penalties with a probability of 2/3.
What is the probability that they score exactly once if they take 5 penalties?
2. (Original post by dewitrydan)
Hey there, I am stuck on the following question, can you help me out please?
Cheers

Suppose a football player scores penalties with a probability of 2/3.
What is the probability that they score exactly once if they take 5 penalties?
Do you know the binomial distribution?
3. No sorry, thats all the info I had on teh question
4. It's binomial with paremters x~b(n=1, p=2/3)
5. X~B(5, 2/3)

P(x=1)

Then use either the tables or the formula
6. Instead of thinking about it as a binomial distribution, you can do it more logically.

If he only scores 1, then he either:

scores the 1st and misses the others
scores the 2nd and misses the others
.
.
scores the 5th and misses the others

What's the probability of each of these? (shortcut: they each have the same probability)
7. (Original post by Daniel Freedman)
Instead of thinking about it as a binomial distribution, you can do it more logically.

If he only scores 1, then he either:

scores the 1st and misses the others
scores the 2nd and misses the others
.
.
scores the 5th and misses the others

What's the probability of each of these? (shortcut: they each have the same probability)
Okay, so they each have the same probability, do you then add the probabilities up?
8. Tree Diagram :P
9. (Original post by dewitrydan)
Okay, so they each have the same probability, do you then add the probabilities up?
Yes.

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Updated: December 23, 2010
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