Dear Applied Statistics Workshop Community,
Our last meeting of this semester will be on Wednesday, May 1 (12:00 EST).
Kosuke Imai presents "Does AI help humans make better decisions? A
methodological framework for experimental evaluation" (joint work with Eli
Ben-Michael, D. James Greiner, Melody Huang, Zhichao Jiang, Sooahn Shin).
<When>
May 1, 12:00 to 1:30 PM, EST
Lunch will be available for pick-up inside CGIS K354.
<Where>
In-person: CGIS K354
Zoom:
https://harvard.zoom.us/j/93217566507?pwd=elBwYjRJcWhlVE5teE1VNDZoUXdjQT09
<Abstract>
The use of Artificial Intelligence (AI) based on data-driven algorithms has
become ubiquitous in today's society. Yet, in many cases and especially
when stakes are high, humans still make final decisions. The critical
question, therefore, is whether AI helps humans make better decisions as
compared to a human-alone or AI-alone system. We introduce a new
methodological framework that can be used to answer experimentally this
question with no additional assumptions. We measure a decision maker's
ability to make correct decisions using standard classification metrics
based on the baseline potential outcome. We consider a single-blinded
experimental design, in which the provision of AI-generated recommendations
is randomized across cases with a human making final decisions. Under this
experimental design, we show how to compare the performance of three
alternative decision-making systems--human-alone, human-with-AI, and
AI-alone. We apply the proposed methodology to the data from our own
randomized controlled trial of a pretrial risk assessment instrument. We
find that AI recommendations do not improve the classification accuracy of
a judge's decision to impose cash bail. Our analysis also shows that
AI-alone decisions generally perform worse than human decisions with or
without AI assistance. Finally, AI recommendations tend to impose cash bail
on non-white arrestees more often than necessary when compared to white
arrestees.
The paper is available on arXiv: https://arxiv.org/pdf/2403.12108.pdf
<2023-2024 Schedule>
GOV 3009 Website:
https://projects.iq.harvard.edu/applied.stats.workshop-gov3009
Calendar:
https://calendar.google.com/calendar/u/0?cid=Y18zdjkzcGF2OWZqa2tsZHJidTlzbm…
Best,
Jialu
--
Jialu Li
Department of Government
Harvard University
*https://jialul.github.io/ <https://jialul.github.io/>*
Dear Applied Statistics Workshop Community,
Our next meeting will be on Wednesday, April 24 (12:00 EST). Siyu Heng
presents "Design-Based Causal Inference with Missing Outcomes: Missingness
Mechanisms, Imputation-Assisted Randomization Tests, and Covariate
Adjustment."
<When>
April 24, 12:00 to 1:30 PM, EST
Lunch will be available for pick-up inside CGIS K354.
<Where>
In-person: CGIS K354
Zoom:
https://harvard.zoom.us/j/93217566507?pwd=elBwYjRJcWhlVE5teE1VNDZoUXdjQT09
<Abstract>
Design-based causal inference, also known as randomization-based or
finite-population causal inference, is one of the most widely used causal
inference frameworks, largely due to the merit that its statistical
validity can be guaranteed by the study design (e.g., randomized
experiments) and does not require assuming specific outcome-generating
distributions or super-population models. Despite its advantages,
design-based causal inference can still suffer from other data-related
issues, among which outcome missingness is a prevalent and significant
challenge. This work systematically studies the outcome missingness problem
in design-based causal inference. First, we propose a general and flexible
outcome missingness mechanism that can facilitate finite-population-exact
randomization tests for the null effect. Second, under this flexible
missingness mechanism, we propose a general framework called "imputation
and re-imputation" for conducting finite-population-exact randomization
tests in design-based causal inference with missing outcomes. This
framework can incorporate any imputation algorithms (from linear models to
advanced machine learning-based imputation algorithms) while ensuring
finite-population-exact type-I error rate control. Third, we extend our
framework to conduct covariate adjustment in randomization tests and
construct finite-population-valid confidence sets with missing outcomes.
Our framework is evaluated via extensive simulation studies and applied to
a cluster randomized experiment called the Work, Family, and Health Study.
Open-source Python and R packages "iArt" (*i*mputation-*A*ssisted *r*
andomization *t*est) are developed for implementation of our framework.
This talk is based on joint work with Yang Feng and Jiawei Zhang. The
working paper is available on arXiv: https://arxiv.org/abs/2310.18556
<2023-2024 Schedule>
GOV 3009 Website:
https://projects.iq.harvard.edu/applied.stats.workshop-gov3009
Calendar:
https://calendar.google.com/calendar/u/0?cid=Y18zdjkzcGF2OWZqa2tsZHJidTlzbm…
Best,
Jialu
--
Jialu Li
Department of Government
Harvard University
*https://jialul.github.io/ <https://jialul.github.io/>*
Dear Applied Statistics Workshop Community,
Just a quick reminder, our next meeting is Wednesday, April 17 (12:00 EST).
Connor Jerzak presents "Selecting Optimal Candidate Profiles in Adversarial
Environments Using Conjoint Analysis" (Joint with Kosuke Imai).
<When>
April 17, 12:00 to 1:30 PM, EST
Lunch will be available for pick-up inside CGIS K354.
<Where>
In-person: CGIS K354
Zoom:
https://harvard.zoom.us/j/93217566507?pwd=elBwYjRJcWhlVE5teE1VNDZoUXdjQT09
<Abstract>
Conjoint analysis, an application of factorial experimental design, is a
popular tool in social science research for studying multidimensional
preferences. In such experiments in the political analysis context,
respondents are asked to choose between two hypothetical political
candidates with randomly selected features, which can include partisanship,
policy positions, gender and race. We consider the problem of identifying
optimal candidate profiles. Because the number of unique feature
combinations far exceeds the total number of observations in a typical
conjoint experiment, it is impossible to determine the optimal profile
exactly. To address this identification challenge, we derive an optimal
stochastic intervention that represents a probability distribution of
various attributes aimed at achieving the most favorable average outcome.
We first consider an environment where one political party optimizes their
candidate selection. We then move to the more realistic case where two
political parties optimize their own candidate selection simultaneously and
in opposition to each other. We apply the proposed methodology to an
existing candidate choice conjoint experiment concerning vote choice for US
president. We find that, in contrast to the non-adversarial approach,
expected outcomes in the adversarial regime fall within range of historical
electoral outcomes, with optimal strategies suggested by the method more
likely to match the actual observed candidates compared to strategies
derived from a non-adversarial approach. These findings indicate that
incorporating adversarial dynamics into conjoint analysis may yield unique
insight into social science data from experiments.
<2023-2024 Schedule>
GOV 3009 Website:
https://projects.iq.harvard.edu/applied.stats.workshop-gov3009
Calendar:
https://calendar.google.com/calendar/u/0?cid=Y18zdjkzcGF2OWZqa2tsZHJidTlzbm…
Best,
Jialu
--
Jialu Li
Department of Government
Harvard University
*https://jialul.github.io/ <https://jialul.github.io/>*
Dear Applied Statistics Workshop Community,
Just a quick reminder, our next meeting is Wednesday, April 10 (12:00 EST).
Melissa Dell presents “Efficient OCR for Building a Diverse Digital
History.”
<When>
April 10, 12:00 to 1:30 PM, EST
Lunch will be available for pick-up inside CGIS K354.
<Where>
In-person: CGIS K354
Zoom:
https://harvard.zoom.us/j/93217566507?pwd=elBwYjRJcWhlVE5teE1VNDZoUXdjQT09
<Abstract>
Thousands of users consult digital archives daily, but the information they
can access is unrepresentative of the diversity of documentary history. The
sequence-to-sequence architecture typically used for optical character
recognition (OCR) – which jointly learns a vision and language model - is
poorly extensible to low-resource document collections, as learning a
language-vision model requires extensive labeled sequences and compute.
This study models OCR as a character level image retrieval problem, using a
contrastively trained vision encoder. Because the model only learns
characters’ visual features, it is more sample efficient and extensible
than existing architectures, enabling accurate OCR in settings where
existing solutions fail. Crucially, the model opens new avenues for
community engagement in making digital history more representative of
documentary history. Beyond OCR, the presentation will also discuss how
large differences in sample efficiency across different neural network
architectures influence the types of learning that are often most suited
towards academic applications, particular for low resource settings.
<2023-2024 Schedule>
GOV 3009 Website:
https://projects.iq.harvard.edu/applied.stats.workshop-gov3009
Calendar:
https://calendar.google.com/calendar/u/0?cid=Y18zdjkzcGF2OWZqa2tsZHJidTlzbm…
Best,
Jialu
--
Jialu Li
Department of Government
Harvard University
*https://jialul.github.io/ <https://jialul.github.io/>*
Dear Applied Statistics Workshop Community,
Just a quick reminder, our next meeting is Wednesday, April 3 (12:00 EST).
Zeyang Yu will present "A Binary IV Model for Persuasion: Profiling
Persuasion Types among Compliers."
<When>
April 3, 12:00 to 1:30 PM, EST
Lunch will be available for pick-up inside CGIS K354.
<Where>
In-person: CGIS K354
Zoom:
https://harvard.zoom.us/j/93217566507?pwd=elBwYjRJcWhlVE5teE1VNDZoUXdjQT09
<Abstract>
In the empirical study of persuasion, researchers often use a binary
instrument to encourage individuals to consume information and take some
action. We show that with the Imbens-Angrist instrumental variable model
assumptions and the monotone treatment response assumption, it is possible
to identify the joint distributions of potential outcomes among compliers.
This is necessary to identify the percentage of persuaded individuals and
their statistical characteristics. Specifically, we develop a weighting
method that helps researchers identify the statistical characteristics of
persuasion types: compliers and always-persuaded, compliers and persuaded,
and compliers and never-persuaded. These findings extend the ”κ weighting”
results in Abadie (2003). We also provide a sharp test on the two sets of
identification assumptions. The test boils down to testing whether there
exists a nonnegative solution to a possibly under-determined system of
linear equations with known coefficients. An application based on Green et
al. (2003) is provided. The result shows that among compliers, roughly 10%
voters are persuaded. The results are consistent with the findings that
voters’ voting behaviors are highly persistent.
Link to the paper: yu_2023local.pdf
<https://arthurzeyangyu.github.io/jmp/yu_2023local.pdf>
<2023-2024 Schedule>
GOV 3009 Website:
https://projects.iq.harvard.edu/applied.stats.workshop-gov3009
Calendar:
https://calendar.google.com/calendar/u/0?cid=Y18zdjkzcGF2OWZqa2tsZHJidTlzbm…
Best,
Jialu
--
Jialu Li
Department of Government
Harvard University
*https://jialul.github.io/ <https://jialul.github.io/>*
Dear Applied Statistics Workshop Community,
Our next meeting will be on Wednesday, March 27 (12:00 EST). Shuangning Li
presents "Experimenting under Stochastic Congestion."
<When>
March 27, 12:00 to 1:30 PM, EST
Lunch will be available for pick-up inside CGIS K354.
<Where>
In-person: CGIS K354
Zoom:
https://harvard.zoom.us/j/93217566507?pwd=elBwYjRJcWhlVE5teE1VNDZoUXdjQT09
<Abstract>
We study randomized experiments in a service system when stochastic
congestion can arise from temporarily limited supply and/or demand. Such
congestion gives rise to cross-unit interference between the waiting
customers, and analytic strategies that do not account for this
interference may be biased. In current practice, one of the most widely
used ways to address stochastic congestion is to use switchback experiments
that alternatively turn a target intervention on and off for the whole
system. We find, however, that under a queueing model for stochastic
congestion, the standard way of analyzing switchbacks is inefficient, and
that estimators that leverage the queueing model can be materially more
accurate. We also consider a new class of experimental design, which can be
used to estimate a policy gradient of the dynamic system using only
unit-level randomization, thus alleviating key practical challenges that
arise in running a switchback.
<2023-2024 Schedule>
GOV 3009 Website:
https://projects.iq.harvard.edu/applied.stats.workshop-gov3009
Calendar:
https://calendar.google.com/calendar/u/0?cid=Y18zdjkzcGF2OWZqa2tsZHJidTlzbm…
Best,
Jialu
--
Jialu Li
Department of Government
Harvard University
*https://jialul.github.io/ <https://jialul.github.io/>*
Dear Applied Statistics Workshop Community,
Our next meeting will be on Wednesday, March 20 (12:00 EST). Anton
Strezhnev presents "A Guide to Dynamic Difference-in-Differences
Regressions for Political Scientists."
<When>
March 20, 12:00 to 1:30 PM, EST
Lunch will be available for pick-up inside CGIS K354.
<Where>
In-person: CGIS K354
Zoom:
https://harvard.zoom.us/j/93217566507?pwd=elBwYjRJcWhlVE5teE1VNDZoUXdjQT09
<Abstract>
Difference-in-differences (DiD) designs for estimating causal effects have
grown in popularity throughout political science. Many DiD papers present
their central results through an "event study" plot - a visualization that
combines estimated dynamic average treatment effects for multiple
post-treatment time periods alongside placebo tests of the main identifying
assumption: parallel trends. Despite their ubiquity, the methods used in
practice for the creation of these plots are not standardized and in many
cases the approaches adopted by researchers can result in misleading
inferences about both the treatment effects and the placebo tests. Building
on and synthesizing recent contributions in the econometric literature on
differences-in-differences designs, this paper illustrates some common
pitfalls through a replication of three recently published papers in major
political science journals. We identify three notable problems related to
the incorrect specification of the baseline comparison time, incorrect
inclusion of "always-treated" units, and sensitivity to effect homogeneity
assumptions. We help provide researchers with additional intuition for the
problems that arise due to effect heterogeneity and for the "contamination
bias" result of Sun and Abraham (2021) through a novel decomposition of the
dynamic event study regression in the style of Goodman-Bacon (2021) that
allows researchers to recover the weights placed on each 2x2 comparison
used to construct the effect estimates and placebos. These weights allow
researchers to gauge the sensitivity of each estimate to potential effect
heterogeneity.
Anton is happy to meet with students and faculty after the talk. Please
reach out to Jialu directly if you want to schedule 1:1 meetings with him.
<2023-2024 Schedule>
GOV 3009 Website:
https://projects.iq.harvard.edu/applied.stats.workshop-gov3009
Calendar:
https://calendar.google.com/calendar/u/0?cid=Y18zdjkzcGF2OWZqa2tsZHJidTlzbm…
Best,
Jialu
--
Jialu Li
Department of Government
Harvard University
*https://jialul.github.io/ <https://jialul.github.io/>*
Dear Applied Statistics Workshop Community,
Our next meeting will be on Wednesday, March 6 (12:00 EST). Amanda
Coston presents "Addressing confounding in decision-making algorithms."
<When>
March 6, 12:00 to 1:30 PM, EST
Lunch will be available for pick-up inside CGIS K354.
<Where>
In-person: CGIS K354
Zoom:
https://harvard.zoom.us/j/93217566507?pwd=elBwYjRJcWhlVE5teE1VNDZoUXdjQT09
<Abstract>
Machine learning algorithms are used for decision-making in societally
high-stakes settings from child welfare and criminal justice to healthcare
and consumer lending. These algorithms are often intended to predict
outcomes under a proposed decision. It is challenging to evaluate how well
these algorithms perform because we only observe the relevant outcome under
a biased sample of the population. In this talk, we explore how to use
techniques from causal inference to estimate performance on the full
population. We will consider several strategies to account for confounding
factors that affect the decision and the outcome. First, we study runtime
confounding where all relevant factors are captured in the historical data,
but it is either undesirable or impermissible to use some such factors in
the prediction model. Second, we study the setting with unobserved
confounders where we can bound the degree to which the outcome varies on
average between units receiving different decisions conditional on observed
covariates and identified nuisance parameters. We develop debiased machine
learning estimators for the learning target and predictive performance
estimands under both settings. We present empirical results in the consumer
lending and child welfare domains.
Papers: arxiv:2212.09844 <https://arxiv.org/abs/2212.09844> and
arxiv:2006.16916 <https://arxiv.org/abs/2006.16916>.
<2023-2024 Schedule>
GOV 3009 Website:
https://projects.iq.harvard.edu/applied.stats.workshop-gov3009
Calendar:
https://calendar.google.com/calendar/u/0?cid=Y18zdjkzcGF2OWZqa2tsZHJidTlzbm…
Best,
Jialu
--
Jialu Li
Department of Government
Harvard University
*https://jialul.github.io/ <https://jialul.github.io/>*
Dear Applied Statistics Workshop Community,
Our next meeting will be on Wednesday, February 28 (12:00 EST). Phillip Heiler
presents "Heterogeneous Treatment Effect Bounds under Sample Selection with
an Application to the Effects of Social Media on Political Polarization."
<When>
February 28, 12:00 to 1:30 PM, EST
Lunch will be available for pick-up inside CGIS K354.
<Where>
In-person: CGIS K354
Zoom:
https://harvard.zoom.us/j/93217566507?pwd=elBwYjRJcWhlVE5teE1VNDZoUXdjQT09
<Abstract>
We propose a method for estimation and inference for bounds for
heterogeneous causal effect parameters in general sample selection models
where the treatment can affect whether an outcome is observed and no
exclusion restrictions are available. The method provides conditional
effect bounds as functions of policy relevant pre-treatment variables. It
allows for conducting valid statistical inference on the unidentified
conditional effects. We use a flexible debiased/double machine learning
approach that can accommodate non-linear functional forms and
high-dimensional confounders. Easily verifiable high-level conditions for
estimation, misspecification robust confidence intervals, and uniform
confidence bands are provided as well. We re-analyze data from a
large-scale field experiment on Facebook on counter-attitudinal news
subscription with attrition. Our method yields substantially tighter effect
bounds compared to conventional methods and suggests depolarization effects
for younger users.
The paper is available on arXiv:https://arxiv.org/abs/2209.04329
<2023-2024 Schedule>
GOV 3009 Website:
https://projects.iq.harvard.edu/applied.stats.workshop-gov3009
Calendar:
https://calendar.google.com/calendar/u/0?cid=Y18zdjkzcGF2OWZqa2tsZHJidTlzbm…
Best,
Jialu
--
Jialu Li
Department of Government
Harvard University
*https://jialul.github.io/ <https://jialul.github.io/>*
Dear Applied Statistics Workshop Community,
Our next meeting will be on Wednesday, February 21 (12:00 EST). Ross
Mattheis presents "Spurious Mobility in Imperfectly Linked Data Trials"
(joint with Jiafeng Chen).
<When>
February 21, 12:00 to 1:30 PM, EST
Lunch will be available for pick-up inside CGIS K354.
<Where>
In-person: CGIS K354
Zoom:
https://harvard.zoom.us/j/93217566507?pwd=elBwYjRJcWhlVE5teE1VNDZoUXdjQT09
<Abstract>
Estimating intergenerational mobility often requires linking data across
multiple sources. However, mistakes in record linkage can introduce biases
in subsequent estimates. This paper re-examines the history of
intergenerational mobility in the United States with emphasis on bias from
imperfectly linked data. In particular, data corrupted by incorrect links
will typically attenuate estimates of linear estimands towards zero. When
the estimand is the intergenerational elasticity of status, this bias will
tend to exaggerate levels of mobility. We propose two complementary methods
to address bias from imperfectly linked data. Building on a large
literature on Bayesian entity resolution, our first approach samples from a
convenience prior and reports the ratio of the posterior and implicit prior
distributions for the target parameter. Our second approach takes advantage
of the availability of repeated measurements and identification results in
settings with misclassified data due to Hu (2008). Consistent with bias
from data-corruption, our estimates suggest that levels of mobility in the
U.S. were lower than previously believed, with conventional estimates of
the father-son elasticity of occupation status 10% to 40% lower than our
estimates. The gap between ours and conventional estimates is largest in
the mid-nineteenth century and declines in more recent years, resulting in
relatively stable levels of mobility over the period.
<2023-2024 Schedule>
GOV 3009 Website:
https://projects.iq.harvard.edu/applied.stats.workshop-gov3009
Calendar:
https://calendar.google.com/calendar/u/0?cid=Y18zdjkzcGF2OWZqa2tsZHJidTlzbm…
Best,
Jialu
--
Jialu Li
Department of Government
Harvard University
jialu_li(a)g.harvard.edu
