Causal claims are best made when we analyse data from experiments (ideally randomized control trials). The randomization process allows you to claim that differences in a measured outcome are likely due to an experimentally allocated treatment, as opposed to some other confounding factor or difference between the test and control groups.
But experiments and randomisation of treatment can be expensive and sometimes impossible. Let's consider just two examples:
Quasi-experimental methods have been developed so that (when certain assumptions are satisfied) we can still make causal claims in the absence of experimental randomisation across treatment units (e.g. people, households, countries, etc.).
CausalPy aims to have a broad applicability to making causal claims across a range of quasi-experimental settings.
CausalPy is still a beta release, it already has some great features. The focus of the package is to combine Bayesian inference with causal reasoning with PyMC models. However it also allows the use of traditional ordinary least squares methods via
At the moment we focus on the following quasi-experimental methods, but we may expand this in the future:
By way of example, we can run a regression discontinuity analysis to examine the effects of reaching legal drinking age (in the USA) upon all cause mortality. With mortality rate data from (Carpenter & Dobkin, 2009) loaded into
df, we can run the analysis like this:
And by calling
result.plot() we get a pretty nice output.
In this observational dataset, there was no random allocation to drinking or no drinking conditions. But the logic is that if we find a discontinuity (which we did) then on balance of probability, it is likely that the legal drinking age is causally responsible, as opposed to some other confounding variable.
We want to share the package with you all at this very early point -
CausalPy could be considered as being in beta stage. So we are interested in your thoughts on the repository, suggestions for features, or bug reports. Once we are at a more stable point in
CausalPy's development then we will open it up for code contributions, but we are not yet at that point.
And check out the package here:
If you are interested in seeing what we at PyMC Labs can do for you, then please email firstname.lastname@example.org. We work with companies at a variety of scales and with varying levels of existing modeling capacity. We also run corporate workshop training events and can provide sessions ranging from introduction to Bayes to more advanced topics.