Explanation and reproducibility in data-driven science (new course)

This is Jessica. Today I start teaching a new seminar course I created to CS grad students at Northwestern, called Explanation and Reproducibility in Data-Driven Science. 

Here’s the description:

In this seminar course, we will consider what it means to provide reproducible explanations in data-driven science. As the complexity and size of available data and state-of-the-art models increase, intuitive explanations of what has been learned from data are in high demand. However, events such as the so-called replication crisis in social science and medicine suggest that conventional approaches to modeling can be widely misapplied even at the highest levels of science. What does it mean for an explanation to be accurate and reproducible, and how do threats to validity of data-driven inferences differ depending on the goals of statistical modeling? The readings of the course will be drawn from recent and classic literature pertaining to reproducibility, replication, and explanation in data-driven inference published in computer science, psychology, statistics, and related fields. We will examine recent evidence of problems of reproducibility, replicability and robustness in data-driven science; theories and evidence related to causes of these problems; and solutions and open questions. Topics include: ML reproducibility, interpretability, the social science replication crisis, adaptive data analysis, causal inference, generalizability, and uncertainty communication.

The high level goal is to expose more CS PhD students to results and theories related to blind spots in conventional use of statistical inference in research. My hope is that reading a bunch of papers related to this (ambitious) topic but from different angles will naturally encourage thinking beyond the specific results to make observations about how overinterpreting results and overtrusting certain procedures (randomized experiments, test-train splits, etc) can become conventional in a field. 

Putting together the reading list (below) was fun, but I’m open to any suggestions of what I missed or better alternatives for some of the topics. The biggest challenge I suspect will be having these discussions without being able to assume a certain series of stats courses (prerequisites call for exposure to both explanatory and predictive modeling, but I left it kind of loose). I am doing a few lectures early on to review key assumptions and methods but there’s no way I can do it all justice.

In developing it, I consuilted syllabi from a few related courses: Duncan Watts’ Explaining Explanation course at Wharton (which my course overlaps with the most), Matt Salganik and Arvind Narayanan’s Limits of Prediction at Princeton, and Jake Hofman’s Modeling Social Data and Data Science Summer School courses.  

Schedule of readings

1. Course introduction

Optional:

2. Review: Statistical Modeling in Social Science

Note: These references are for your benefit, and can be consulted as needed to fill gaps in your prior exposure.

3. Review: Statistical Modeling in Machine Learning

Note: These references are for your benefit, and can be consulted as needed to fill gaps in your prior exposure.

PROBLEMS AND DEFINITIONS

4. What does it mean to explain?

5. What does it mean to reproduce? 

Optional:

6. Evidence of reproducibility in social science and ML

Optional:

PROPOSED CAUSES

7. Adaptive overfitting: social science

Optional: 

8. Adaptive overfitting: ML

Optional:

9. Generalizability

Optional:

10. Causal inference

Optional:

11. Misspecification & multiplicity

Optional:

12. Interpretability: ML

Optional:

13. Interpretability: Social Science

Optional:

 

SOLUTIONS AND OPEN QUESTIONS

14. Limiting degrees of freedom

Optional:

15. Integrative methods

Optional:

16. Better theory

Optional: 

17. Better communication of uncertainty 

Optional:

18 thoughts on “Explanation and reproducibility in data-driven science (new course)”

  1. This class looks amazing and has several resources and perspectives beyond the ones that typically get covered that I appreciate the links to learn more about.

    On the topic of forking paths and adaptive overfitting, following up on the Dwork et al analysis, I would maybe mention something about Littlestone dimension, which is quite literally, as a sequential version of shatter dimension over trees, a way of quantifying forking, and its effects on generalizability and prediction, viz, that worst case prediction errors can fail to converge for classes with unbounded Littlestone dimension, which include many classes (eg, VC) for which classical learning theory suggests overfitting should not be a problem. For an introduction I like Shalev-Shwartz Ch. 3

    The reason I think it’s worth bringing up is that equivalence results show that many proposed solutions to preventing adaptive overfitting are equivalent to bounding this dimension, either through explicit online learning approaches (which have a flavor of accounting for nonstationarity) or by recent results showing equivalence to differential privacy https://t.co/IpmNF7nXzW, which can then be generated in a variety of ways, including holdouts, noise, Bayesian sampling (https://www.jmlr.org/papers/volume18/15-257/15-257.pdf), etc.

    I think that strand of work is only a piece of the puzzle on those topics (where do model classes come from? What kinds of adaptivity are actually common beyond the worst case and how do we address them scientifically, socially, etc?), but the rest of the syllabus seems to cover what’s known about those quite well.

  2. Great title for the course too. Titles are important. I like the idea of generalization (poststratification, etc.) being part of reproducibility. It’s a good framework. Thinking in very general terms, we can even think of the idea of a “parameter” in a parametric model as representing reproducibility, in that a parameter is what persists from one problem to the next. This is related to the point that Bois, Jiang, and I made in our paper from 1996 that substantively-motivated (rather than merely phenomenological) models play well with Bayes, for two reasons:
    1. In a substantively-motivated model, the parameters have a meaning external to the data at hand, which makes it more reasonable to think we can come up with good priors for them.
    2. If a model is parameterized well, the parameters will be roughly constant from person to person, or from scenario to scenario, so that a hierarchical model allowing variation will do lots of partial pooling, giving stable estimates.

  3. This is a great course! So many great papers to comb through and mull over.

    As a practitioner of ML in healthcare, I do wish there was a better source of material for “OMG don’t do that”, good anti-patterns for models. One anti-pattern that would seem to fit into the lack of generalizability in your course is models that are built on poorly chosen surrogate variables as found in Obermeyer, https://www.science.org/doi/10.1126/science.aax2342 .

    But to me this is not just a lack of generalizability of the original model, but a profound miss-specification due to the challenge of collecting data for the real outcome variable. The model fit something other than the use case required, but most of the testing and other checks yielded false positives because they also checked against the poor surrogate outcome.

  4. Thanks for sharing your reading list! It looks very comprehensive, and I intend to check it out in greater detail.

    One thing that I noticed on a cursory look over the reading list is that it has a lot of content about statistical methods and theory, but I didn’t find anything about the more mundane aspects of reproducibility from the software perspective. Things like how running the same analysis with different versions of libraries or software packages can yield different results, or how multiple runs stochastic algorithms can produce different outputs, etc.

    I would be interested to hear why you chose to leave that out of the course. Are these topics things that your audience is already familiar with and do not need to be covered again? Or is there a different reason for not covering them?

    Thanks!

  5. What a terrific looking course. Bookmarking a lot!
    I don’t know how much computer science PhD students really understand about where data come from or how social science data are collected. I might want to suggest some “classics” including maybe Campbell and Stanley https://wagner.nyu.edu/files/doctoral/Campbell_and_Stanley_Chapter_5.pdf
    and maybe Fisher since basically almost all social science statistics books still follow the basic structure of Statistical Methods for Research Methods and Design of Experiments. I feel like if you don’t understand how these works have shaped social science research some of the other works are decontextualized.
    You might want a general research methods text as a reference. Or maybe just some resources on specific methods. A lot of people think it takes 10 minutes to write a survey
    I just was poking around and saw this https://theoryandscience.icaap.org/content/vol7.1/denis.html which has a nice bibliography and an overview of one strain of work.

  6. Hi Jessica, That’s a great collection of topics and references.

    I’d like to mention some work I did with Masayoshi Mase (Hitachi, Ltd.) and Ben Seiler (Stanford stat PhD student).

    https://arxiv.org/abs/2205.15750

    We discuss the variable importance part of interpretability as a problem of `causes of effects’ vs `effects of causes’. So it remains hard even if the causal knowledge is complete and correct. We compare methods by properties, such as whether the cost is exponential, whether they have to use previously unobserved variable combinations, whether it is possible to attribute importance to variables that the model does even use, whether the method requires user input, and so on. We do an extended worked example on the COMPAS data to illustrate our proposed cohort Shapley method.

    Ultimately, setting variable importance is going to require interacting with the problem domain. We don’t think of it as something that can or should be done automatically.

    • Art:

      Regarding “causes of effects” vs. “effects of causes,” I recommend this paper with Guido, “Why ask why? Forward causal inference and reverse causal questions.” It never got published on its own, but I stuck it in as Section 21.5 of Regression and Other Stories.

      • I like that you can use those attribution issues to focus the next effects of causes investigation. So then as you and Guido say, it is not cocktail party chatter.

        However there are settings where the `next thing’ is not pertinent. For instance, there could be a lot of interest in why a given person had a loan declined, or was predicted to reoffend, or was deemed appropriate for the ICU, in each case by an algorithm that could be rerun with different values for a subset of the person’s variables.

        I found this article useful:

        Dawid AP, Musio M. Effects of causes and causes of effects. Annual Review of Statistics and Its Application. 2022 Mar 7;9:261-87.

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