The mean of two single large sample 1000 and 2000 member are 67.5 inch and 68.0 can sample b regarded as drawn

Question

(the question continue)from the same population with standard deviation 2.5 inch?

plss answer in detail

Answer 1

The concept you are looking for is the "standard error":
http://en.wikipedia.org/wiki/Standard_error_%28statistics%29

If your sample size is N and the standard deviation of the population is S, then the standard error is:

E = S/sqrt(N)

This standard is a measure of how far the mean of the sample is from the underlying mean of the population.

In particular. it is the standard deviation of the sampling process: if you took many samples of N elements from the same population and computed the sample means, you'd get a normal distribution with standard deviation E

In your case, you can compute E for the two sample sizes and determine the the difference between their means in terms of the two Es. Then you can decide whether the two means are too many standard deviations apart to be from the same population.

Just where you draw the threshold is up to you. Typical values are at the 95% confidence level (1.96 standard deviations) and 99% (2.58 standard deviations), but choose whatever value you like.

http://en.wikipedia.org/wiki/Normal_distribution