Sample size and documentation for discriminant analysis

Question

Does anybody have good documentation for discriminant analysis? I have 9 variables (measurements), 60 patients and my outcome is good surgery, bad surgery. Also, is my sample size too small? Thank you

Answer 1

I have 3 points to say. First, what is "good" documentation for you? There is a lot of pages on DA and downloadable books on multivariate statistics (where DA is discussed) in the Internet. Some texts are superficial and easy, some are more sophisticated.

Second, because you have just 2 groups your DA will be virtually equivalent to the multiple linear regression with "Groups" dependent variable and your 9 variables as independent variables. The results (coefficients) after DA and the regression will be proportional between the two analyses. So, if you know linear regression that will suffice to understand the results even if you don't know DA.

Third, whenever there is just two groups it is worth considering to prefer binary logistic regression to DA. The logistic regression is less hard-to-plese in regard to assumptions than DA is. Just to mention some: it doesn't require multivariate normal distribution; it doesn't require equality of variances-covariances between the groups; it is less sensitive to disproportion of groups sizes as well as to outliers.