Central Limit Theorem: Fisheries Management

[majin]

just a query... does anyone have a general definition of the central limit theorom. I've been looking on the internet and all I've got is a whole lot of complex crap

P.S it would help if it was related to fisheries management

 

[marcmtlca]

simply put: under certain regularity conditions (finiteness of mean and variance), given Y_i are independent and identically distributed random variables.

\frac{\sqrt{n}}{\sigma}(\frac{1}{n}\sum_{i=1}^{n}Y_i-\mu) \rightarrow N(0,1)

You can think of the Y_i as fish that you are sampling from a population of fish who's mean age and variance you know. Then if you sample a large amount of fish. The average age of your sampled fish standardized as above will be approximately normal(0,1).

 

[FunkyDwarf]

the one we were taught is that sqrt(n)(X-u)/(s) - >N(0,1) if s>30 otherwise you got to use the t distribution where s is the sample std deviation

 

[marcmtlca]

ya so if your n is not large enough, the approximation is not comfortable enough to use the normal. that's fine.

 

[FunkyDwarf]

yeh so as n->infinity the t distrubution tends to the normal