fboehm / chick2016

chick2016

Goals

The goals of my analysis are to understand the distinctions between 1) the "LOD difference" statistic (my terminology) that Chick et al 2016 use and 2) the Baron-Kenny approach, as described in vanderWeele's text (Chapter 2).

It's not obvious to me, at first glance, that there is an equivalence between the two approaches. vanderWeele describes the Baron & Kenny approach as requiring two regressions, Y ~ M + A and M ~ A, for exposure A, mediator M, and outcome (target) Y.

Chick et al. (2016) use a LOD difference statistic. This requires four regressions. First, they calculate the LOD by comparing likelihoods for these two models:

Y ~ A v Y ~ 1

Then, they fit two additional models:

Y ~ A + M and Y ~ 1 + M

Each pair of models above gives a LOD score. They then calculate the difference of these two LOD scores as their summary statistic.

Chick, Munger, et al. (2016) data and scripts

Data and R scripts downloaded, on May 4, 2019, from: https://churchill-lab.jax.org/website/data/Chick_Nature_2016/