Number of observations for logistic regression

[freedom93]

Hello,

I'm new SAS user; I performed a logistic regression of 68 observations, but this is not significant. A friend advised me to take two or three times the number of observations that I have is to say the same thing but in two or three times. When I do this, then the regression is significant. But have I the right to do so?
If not, what can I do? I think this is my échatillon of studies was small.

[PGStats]

Don't do that. One of the key assumptions for inference in logistic regression is the independence of observations. Duplicated obs are definitely not independent.

What you can do:

• Plot the data. Make sure there are no outliers.
• Consider using another statistical model.
• Get more independent data.

Good luck.

[ballardw]

How many independent variables are you using? How many levels are there for each of those? Too many varaibles/levels will often leave nothing signficant as there are not enough observations in any group.

Also, models are NOT required to have a signficant difference. The fact that there isn't may well mean that there is not sufficient influence on the population from your variables.

[Reeza]

This implies that your study was under powered, you didn't have enough samples to find a significant difference - based on the observed difference. 

[Ksharp]

You have small sample data. Try EXACT logistic regression.