Smoking and Cancers: Case-robust Analysis of a Classic Data Set.

A typical structural equation model is intended to reproduce the means, variances, and correlations or covariances among a set of variables based on parameter estimates of a highly restricted model. It is not widely appreciated that the sample statistics being modeled can be quite sensitive to outliers and influential observations leading to bias in model parameter estimates. A classic public epidemiological data set on the relation between cigarette purchases and rates of four types of cancer among states in the USA is studied with case-weighting methods that reduce the influence of a few cases on the overall results. The results support and extend the original conclusions; the standardized effect of smoking on a factor underlying deaths from bladder and lung cancer is .79.