Statnotes collection from NCSU

For a nice applied collection of notes for multivariate analysis, see G. David Garvin's Statnotes. These notes are part of a graduate course, "Quantitative Research in Public Administration" at North Carolina State University (NCSU). Many of the entries include a FAQ section, as well as links to software and a list of references. All this on top of clear explanation of the principles for each topic.

Beware of bias-amplifying covariates!

While I am collecting pointers to good discussions of adjusting for non-random selection with weighting, there is a recent discussion about the inclusion of instrumental variables and the problems that they can cause. The post is here on Andrew Gelman's blog - the discussion that follows is very helpful as well.

Judea Pearl on IPW - a great find!

Judea Pearl's recent post on the intuition behind inverse probability weighting (IPW) is not likely to be one that I send out to non-statistical collaborators, but I did find it very useful for applied statisticians who want to understand current statistical thinking on the theoretical basis for IPW, and how that should guide selection of variables to include in a model for the probabilities in question.

For anyone who is working with observational studies, where selection to treatment is non-random; or with analysis of survey data, where response rates are a concern and non-response bias is possible, the technique of re-weighting the observed data to compensate for the observational design is worth a good look. Guidance on how to think about the models is much needed- and I believe that this post goes a long way towards providing that guidance! I hope to post an application note or two once I've made some headway on at least two projects where this will be useful.