# Need some clarification with statistics

1. Nov 2, 2009

### anjunabeats

Im currently doing an introductory stats course and have learnt:

- poisson distribution
- binomial distribution
- normal distribution
- t-student
- and chi-square

I think I know what most of them look like but am having a bit of a hard time distinguishing what distribution to use when faced with questions.

Heres my current understanding:

- poisson distribution - when pop mean is given over an interval?
- binomial distribution - when given sample size and p of success
- normal distribution - n >30 or if normal
- t-student - when population is normal distributed but variance parameter is unknown
- and chi-square - not too sure when to use.

Wondering if anyone can help me with my current problems, thanks in advance!

2. Nov 3, 2009

### zli034

the normal distrubuted population's random estimated variance is chi square distribute, when you ask what probability you can obtain a variance you need chi square.

3. Nov 3, 2009

### bpet

Firstly, is the goal here to pass the exam or to learn statistics?

4. Nov 3, 2009

### anjunabeats

To learn statistics, im already doing well enough to pass the exam. Im probably going to learn much more difficult concepts in the future so its best if i get the fundamentals right.

5. Nov 4, 2009

### bpet

The key is understanding what assumptions are reasonable for the given data, and which are necessary in order to use a particular distribution in your repertoire. There aren't any fixed rules as to what applies when, but as you learn more distributions and see the various ways they arise you'll gain a more intuitive understanding of which candidates are most suitable for each situation.

Good luck with your studies!

6. Nov 5, 2009

### anjunabeats

thanks for pointing out the obvious.

7. Nov 5, 2009

### bpet

Glad you appreciate the point - many don't, which is why so much dodgy research gets published.

Regarding the original questions, it sounds like you're on the right track except maybe the Poisson distribution - not sure what you meant by "pop mean is given over an interval", did you mean to say "average occurrence rate is given over an interval"?

8. Nov 5, 2009

### anjunabeats

Yeah i think i understand poisson distribution more clearly now, just finished the course today probably planning to learn more chunkier stats in the future.