estimate of population standard deviation! please help!?

Question

consider the following sample of three scores: 2, 4, and 6. the best estimate of the population standard deviation would be.. what? im so confused. please help me!

thank youu!

Answer 1

Lets start out from the beginning.
Our average of this set = 4
Now, we take the set and subtract it against the average.
= -2,0,2

Now, we square those numbers
=4,0,4

Now we add those squared numbers together
= 8

Now, we divide by 3 (our amount of numbers, called n)
= 8/3

Now, take the square root of above number
= sqrt(8/3)
about 1.6329

So we have the following
Mean = 4
Sigma = 1.6329

added note: Sigma (small Greek that looks like a tilted 6) is the symbol of standard deviation. The big Greek sigma symbol looks like a forked E that stands for summation. They are NOT mathematically the same.

Answer 2

Estimate Population Standard Deviation

Answer 3

n = 3
m = 4
var = 8
sample σ = √8/3 ≈ 1.632993
Estimated Population σ = √(8/(3 - 1)) ≈ 2

Answer 4

Of course it is. The population standard deviation uses the same formula as the sample SDEV, but instead of dividing the variances by "n-1", divide it by the population, "n". You can use the population St.Dev on any "sample size" greater than n=30 (or, as I use it, n=50). This is a corollary from the Central Limit Theorem. EDIT: The CLT says that "for any sample size greater than 50, the distribution can be approximated by a Gaussian distribution". Good luck with your sampling, Matthew