[R] Comparison of demographics between 2 study samples

[Bernardo Rangel Tura]

Em Qua, 2008-08-13 às 19:14 -0700, Mark Home escreveu:
> Dear All:
> 
> I have a clinical study where I would like to compare the demographic information for 2 samples in a study.  The demographics include both categorical and continuous variables.  I would like to be able to say whether the demographics are significantly different or not.
> 
> The majority of papers that I have read use multiple techniques to achieve this (e.g., t-test for the continuous variables and either Fischer exact or Chi-square for categorical).  I wonder whether this might lead to spurious differences due to multiple significance tests.  Is there a better way to do this?
> 
> Thanks in advance for your advice,
> 
> Mark

Mark,

You need make multiple comparison correction.

The most know correction is Bonferroni.

In this case you make 

new p value = alpha/n  where alpha is "alpha" of planning your study and
"n"  is a number of test you using.

Example

If may clinical study have a alpha = 0.05 and i make 10 test my ne
p-value is 0.05/10 = 0.005



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Tura