Standard error of the mean

Worked example

We will use the small sample of lamb PCVs again.

Lamb No.	PCV
1	33
2	26
3	29
4	32
5	31
ΣY	151

We calculate the estimated standard error, as the standard deviation of the observations (previously calculated as 2.775) divided by the square root of the number of observations (√5).

SE()   =   2.775   =   1.241 √5

This is the value of the standard error we should use if we intend to carry on and calculate confidence limits. If however we intend to quote standard errors, we should use the corrected estimate of the standard deviation (previously calculated as 2.953).

Hence

SE()corr.   =   2.953   =   1.321 √5