# How to decide between a logistic regression or conditional logistic regression?

I have a case-control study in which the cases are firms with health insurance and the controls are firms with no health insurance. I am studying the factors affecting enrolment in health insurance and was therefore using a logistic regression, which includes several covariates on firm characteristics that were measured in a survey. I have randomly sampled the firms from a database that includes two strata: insured and uninsured firms. I selected 65 from each group. However, within the group I also sampled from four strata that correspond to industry. I am therefore wondering if I need to use conditional logistic regression, as opposed to unconditional logistic regression. However, I was under the impression that conditional logistic regression was for matched case-control studies or panel studies. In other feedback I've received I've been told that because I sampled on the outcome, I need to use the conditional model. Could someone please help me figure out which m? Any references would also be much appreciated. Thank you.

• Could you clarify how you sample from the four industry strata? Did your sampling scheme specify that you picked a certain number from each stratum? Also do you have data at the employee level or only at the company level? Feb 14, 2011 at 7:57
• I first divided each stratum (insured and uninsured) by industry (4 groups). Within these industry groups I further divided the sample into 4 groups that correspond to the size of the company. This was to ensure that I collected similar numbers within each industry and that i didn't up with only small firms. I then numbered all observations and used quota sampling with a random number generator to select firms from each of the 32 groups. I used sampling weights in the analysis to ensure that each observation was weighted by the inverse of the probability of being selected. Feb 14, 2011 at 15:58
• No, I don't look at any employee level data within the sample. I realize that my sampling is probably not the best but I was mainly interested in getting some descriptive results. However, I'd also like to be able to use the logistic regression analysis to understand the factors affecting whether or not a company enrolls in health insurance. Thank you! Feb 14, 2011 at 15:58
• Clarification: I wrote that I used quota sampling but it was in fact stratified sampling. Feb 14, 2011 at 19:32