When the repetitions of each treatment group are not equal (unbalanced data), SEM should be expressed as "combined SEM".

How to calculate aggregate SEM in the paper?

Literature 3

In SPSS analysis:

(1) When the number of repetitions is unequal (unbalanced data), SEM is the average value of "standard deviation" in the output result of "Option-Descriptive Statistics" of SPSS (because each treatment group is unequal). For Example 2, the combined SEM = (1.388+1.267+1.267+1.388)/4 =1.328.

In SAS analysis:

(2) When the number of repetitions is unequal (unbalanced data), SEM is the average of the "standard deviation" in the output result of SAS "least square mean" (because each treatment group is unequal).

Effects of Four Feeds on Weight Gain of Piglets

Group weight gain (kg)

1 47 47 44 42 42

2 33 39 4 1 33 34 35

3 23 25 23 29 28 20

4 28 24 25 20 23

SPSS output results:

Only a part is intercepted, and the content is very long. You can go to the original article to see the calculations of SD, SE, SEM and Pooled SEM.