Simple probability or more advanced technique?

Hi everyone, I have two questions regarding a homework question (set out below):

- Can this question be addressed using simple probability or is a more advanced probability technique required (e.g. using a probability distribution)?
- What does “include the endpoints” mean? (This term is confusing me because I don't think it is normally used in simple probability calculations).

Thanks in advance.

Homework question:

15%of car crashes result in severe injury to at least one person involved in thecrash. If there are 25 major car crashes per month, calculate the followingprobabilities:

in 25 major crashes, exactly five result in severe injury

in 25 major crashes, between two and eight result in seriousinjury? (*include the endpoints*)

in 25 major crashes, no severe injuries occur

in 25 major crashes, at least one severe injury occurs

Re: Simple probability or more advanced technique?

Depends how you define advanced.

I teach the binomial distribution to final year high school students here in Oz. They seem to understand it.

Your problem is binomial with p=0.15 and n=25. Let X be the occurrance of a serious injury.

Note $\displaystyle P(X=k) = \binom{n}{k}p^k\times (1-p)^{n-k}$

For the first question find P(X=5)

For the second find P(X=2)+P(X=3)+...+P(X=8)

For the third find P(X=0)

For the forth P(X>0) = P(X=1)+P(X=2)+...+P(X=25) or even easier 1-P(X=0)

Does this help?

Re: Simple probability or more advanced technique?

Quote:

Originally Posted by

**pickslides** Depends how you define advanced.

I teach the binomial distribution to final year high school students here in Oz. They seem to understand it.

Your problem is binomial with p=0.15 and n=25. Let X be the occurrance of a serious injury.

Note $\displaystyle P(X=k) = \binom{n}{k}p^k\times (1-p)^{n-k}$

For the first question find P(X=5)

For the second find P(X=2)+P(X=3)+...+P(X=8)

For the third find P(X=0)

For the forth P(X>0) = P(X=1)+P(X=2)+...+P(X=25) or even easier 1-P(X=0)

Does this help?

Thanks so much - this has been very helpful.