Confusion!!

#1
Hello,

I am new to stats and have a couple basic questions regarding sampling , the central limit theorem and probability.

If the sample size is 30 or greater then the sample means follow a normal distribution.I wanted to know the minimum size of the observations in each sample and its limits. Can I take 30 samples each having 2 observations with the knowledge that the means of these samples would follow a normal distribution?

Also I would like to get an intuition about probability distributions. What is the fundamental difference between probalility distruibutions and frequency distributions?

Can anyone please let me know about these as I am not able to progress much without getting my basics clear :)

Thanks

Viv
 

JohnM

TS Contributor
#2
The distributions of both observations should be normal, or close to it.

The difference between a probability distribution and a frequency distribution is that a prob dist displays a probability (between 0 and 1) for each possible outcome.

A frequency distributiuon displays the frequency of each outcome "bin" - a bin typically contains >1 outcome. If it's a relative frequency dist, then it will display the probability or percentage of observations in each bin.