How to derive standard deviation from standard error


SD=Standard error * sqrt(N);




QC: I checked the algorithm using SAS. The result was consistent with the algorithm (i.e., SD=standard error*sqrt(N)).

proc means data=sashelp.class mean std stderr n; var height; run;

ƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒ Mean 62.3368421

SD 5.1270752

Stadard Error 1.1762317

N 19 ƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒ

SAS T-test for proportions

data YesNo; input Gender $ NumYes Total; Response="Yes"; Count=NumYes; output; Response="No "; Count=Total-NumYes; output; datalines; Men 30 100 Women 45 100 ;

proc print noobs; var Gender Response Count; run;

proc freq order=data; weight Count; table Gender * Response / chisq riskdiff; exact riskdiff; run;

How to QC the result of random assignment

QC 1:

Check the number of cases within each group (i.e. treatment and control group).


Check if the number of treatment school and control school is balanced within block.



Cronbach's alpha

The UCLA site explains Cronbach's alpha as the average internal correlation among survey items. It also says that it is not a measure of unidimensionality. Rather, it is a measurement of internal consistency (though just intuitively I feel what is coherent tends to be also uni-dimensional… I think the point is that the measure is […]

Sample size calculation using Excel sheet

I wrote this Excel program to calculate sample size for surveys. size calculation 11 30 2015.xlsx


Excel function to replicate t-test off SAS PROCs (e.g., GLIMMIX)

Phil of SAS helped me identify this function. Thank you.

T-test conducted in PROC GLIMMIX (or most likely other regression procedures) is expressed in Excel function as:


where T_value must be an absolute value of the original t-value (e.g., if -2 then 2).

This expresses CDF (cumulative distribution function), not […]