01 / Course introduction
WashU Olin Business

AI/ML for Applied/Empirical Research in Business

Dennis J. Zhang

Singapore

Dennis J. Zhang · AI and Business001
01 / Course introduction
WashU Olin Business

This Course

Slides will NOT be shared, so please take notes.

Please DO NOT take photos.

We will focus more on methodology rather than applications

We will focus more on intuition rather than math -- many details will be omitted due to the time constraint.

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02 / Assumed background
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Assumed background: engineering

Prior hands-on experience with AI/ML is assumed.

Building and using models

You know the main AI/ML tasks and model families, including supervised learning, unsupervised learning, and generative AI.

You have worked with data preparation, model training or adaptation, and evaluation on held-out data.

Evaluating a workflow

You recognize overfitting, data leakage, and the role of model selection and validation.

You can assess predictive performance alongside data quality and computational constraints.

We will build on this experience to examine how AI/ML can support applied/empirical research in business.

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Assumed background: mathematics

You are comfortable reading the mathematical formulation of a learning problem.

Mathematical and statistical tools

Working knowledge of linear algebra, calculus, probability, and statistics.

Familiarity with random variables, expectations, conditional relationships, regression, and estimation.

The language of learning

Models and parameters; loss functions, empirical risk, and regularization.

Gradient-based optimization, bias–variance trade-offs, and out-of-sample generalization.

Our starting point is applied/empirical research: questions, measurement, identification, and evidence.

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03 / ML in applied/empirical research
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What is Applied/Empirical Research?

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Applied/Empirical Research

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ML for Research

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ML as Data Source

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ML as Data Source

Every information that is recordable but not numerical can be analyzed with ML to answer business questions

Classified by categories:

Text – NLP

Image – CV

Video – CV

Sound – DL

Biometrics – Bioinformatics

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ML as Data Source

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ML as Data Source

Machine Learning is used to define new variables from unstructured data

Audio data: Analyzing voice data to gain additional information besides length of calls.

“The Power of Voice: Managerial Affective States and Future Firm Performance,” William Mayew and Mohan Venkatachalam, Journal of Finance, 2012.

“Toward Machines with Emotional Intelligence,” Roslind W. Picard, MIT Media Laboratory report.

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ML as Data Source

Machine Learning is used to define new variables from unstructured data

Image data: Analyzing image data to gain additional information besides length of calls.

“How Much Is An Image Worth? An Empirical Analysis of Property’s Image Aesthetic Quality on Demand at AirBNB,” Management Science.

Video data: Analyzing video data to gain additional information of digital ads:

“First Law of Motion: Influencer Video Advertising on TikTok”, Marketing Science

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ML as Data Source

If you are using ML to process text data, this reading is good

Dell, Melissa. "Deep learning for economists." Journal of Economic Literature 63.1 (2025): 5-58.

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ML as Data Source

Reasons to use ML to understand unstructured data:

Cost reduction and Scalability

Objectivity

Built-in other prediction systems

Problems of using ML to understand unstructured data

Measurement Errors

Interpretation

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ML for data processing

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Some problem in OLS illustrated

Y = a + b * D + g(X) + epsilon

Outcome

Y can be generated through ML with error

Treatment:

D can be generated through ML with error

Control:

X can be generated through ML with error

X can be selected by ML with error

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ML as Prediction Error

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Classic Measurement Error and ML Error

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The bias can be arbitrary

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Better model can mean worse error

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Empirical models will not help

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Solution

Two general approaches

Standard error re-computation (Instrumental Variable)

De-biasing

But how?

Remember we have training data.

Using training data to learn a better mapping on the error structure

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Solution

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Solution

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ML can also serve as control variables

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How to Work With Unstructured Data?

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Embedding then Inference

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Research Questions

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Data Generation Process & Estimation Problem

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Step 1: Learn Embedding via Reconstruction

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Step 2: Control for the Embeddings

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Embedding-then-Inference is Inconsistent

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Misaligned Objectives to be Blamed

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Debiased Embedding: Neyman Orthogonal Score

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Debiased Embedding: Aligning Objectives

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Simulation 1: Simple Data Generation Process

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Simulation 1: Embedding-then-Inference

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Simulation 1: Direct Adjustment with DML

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Simulation 1: Comparison

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Last, ML as Data Source does not need Causal Inference

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ML as Research Methods (Causal Inference)

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Causal Inference

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Rubin Causal Model

Rubin causal model tells us that we cannot observe the causal effect from observational data (potential outcome is not observable)

We do not observe what happens to Switzerland if people there do not consume chocolate… We also do not observe China/India if people there have a tradition of consuming chocolate…

We have to rely on averages, but averages will give us biases.

We can compare countries with high and low chocolate consumptions, but these countries are inherently different, which creates biases.

When we have random assignments (an experiment), outcome and baseline biases are gone and we can simply compare the treated and control units.

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Randomized Control Trials

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Average Treatment Effect

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Golden Standard

We typically say experiments are golden standards for causal inference.

Why?

The estimator is simple

It achieves the sqrt-n efficiency

It is unbiased in small samples

Basically it suits to tell a causal story

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But RCTs can easily be invalid

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Go back to our original problem

We have three assumptions essentially to make the above problem super easy:

1. IID of samples

2. SUTVA

3. Random Treatment Assignment

Now, let us try to relax them gradually

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What if we do not have randomness?

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Aggregating Difference-in-Means Estimators

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Aggregating DiM is just Propensity Score

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Unconfundedness

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Unconfoundedness

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ML as Causal Inference

It is hard:

Cross-validation cannot be directly applied to hyper-parameter tuning for causal inference models (Athey and Imbens 2016)

Good performance in predicting the propensity score or outcomes cannot be directly translated into good causal performance (Belloni and Chernozhukov 2014)

Regularization in ML will introduce additional biases (Belloni et al. 2016)

What are the core problems in causal inference?

Non-overlapping/balance, unconfoundedness, power, functional-forms etc.

ML will not magically solve these fundamental problems

ML specifically targeting functional form problems

This is a very fast evolving field (compared to other fields in econometrics)

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ML as Causal Inference – Functional-form relaxation

Observational Studies:

Functional form relaxation: ML is used to search for complex functional relationships between features and outcomes. In Causal Inference, we typically assume linear or simple nonlinear relationships. Can we use ML to select better functional forms?

Relax function forms in Regression Analyses:

Chernozhukov, V., Chetverikov, D., Demirer, M., Duflo, E., Hansen, C., & Newey, W. (2017). Double/debiased/neyman machine learning of treatment effects. American Economic Review, 107(5), 261-65.

Relax function forms in DiD-type of estimators: too many variables we can control, what can we do?

Athey, S., Bayati, M., Doudchenko, N., Imbens, G., & Khosravi, K. (2021). Matrix completion methods for causal panel data models. Journal of the American Statistical Association, 1-15.

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ML as Causal Inference – Functional-form relaxation

Observational Studies:

Variable Selection: ML is developed to select the best set of predictors for out-of-sample performance. In causal inference, we often must select variables by hand/experience. ML will help us to solve this problem more systematically

Variable selection in IVs: too many IVs, what can we do?

Belloni, A., Chen, D., Chernozhukov, V., & Hansen, C. (2012). Sparse models and methods for optimal instruments with an application to eminent domain. Econometrica, 80(6), 2369-2429.

Variable selection in Controls: too many variables we can control, what can we do?

Belloni, A., Chernozhukov, V., & Hansen, C. (2014). Inference on treatment effects after selection among high-dimensional controls. The Review of Economic Studies, 81(2), 608-650.

Variable selection in HTEs: too many dimensions, what can we do?

Wager, Stefan, and Susan Athey. "Estimation and inference of heterogeneous treatment effects using random forests." Journal of the American Statistical Association 113.523 (2018): 1228-1242.

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Today’s focus

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What the paper does?

It provides a general framework for estimating treatment effects using ML methods

The framework requires:

Some regularity condition

ML estimator to converge at n^-1/4 (which you should realize is slower than n^-1/2 and most parametric models, according to delta method, converge at n^-1/2)

The framework outputs:

N^-1/2 – consistent estimator: means that the distribution of the estimator converges in probability to the true estimator with rate n^-1/2.

Many estimators you learnt in parametric world has this properties.

In frequentist world, converge in probability typically also means asymptotically normal, which means you can easily construct standard errors.

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Let us look at a very simple example

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Partial linear model

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Partial linear model

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Partial linear model: Naïve Approach

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The resulting estimator is biased

Two sources of biases as described by the authors:

Regularization bias:

The ML model cannot perfectly predict the function fast enough according to existing data.

This is fixed by orthogonality moment conditions (this is why the paper is also called Neyman orthogonality)

Overfitting bias:

The ML model may be biased by the existing data compared to the true distribution

This is fixed by sample splitting (very similar to cross validation, which is the key idea in this paper)

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Regularization Bias

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Regularization Bias

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Regularization Bias

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Regularization Bias

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Regularization Bias

Orthogonality will help us to get rid of b.

The idea is not new. It appears in Robinson (1988) and Frisch-Waugh-Lovell theorem (1930)

More recently, it appears on the authors’ prior paper: Belloni et al. (2014) using lasso

The basic idea is to train two machine learning model and double selecting out the biases. This is called double selection in Belloni et al. (2014).

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Frisch-Waugh-Lovell Theorem

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Robinson (1988)

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FWL and Robinson 1988

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DML (2018)

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The description in the paper

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Now the estimator becomes

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Final algorithm for partial linear models

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A more general framework

Now, we just cover the illustrative example of paper

Let us look at the real meat in the paper: a general framework in solving this kind of problem

Again, we will use partial linear as an example, and will generalize later

Why does it matter?

We can then change the idea to fit into other problems that is not a simple causal evaluation

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A more general framework

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Score function

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Neyman Orthogonality

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DML

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DML

The authors show that the estimator through this procedure will

Require:

Some regularity condition

ML estimator to converge at n^-1/4 (which you should realize is slower than n^-1/2 and most parametric models, according to delta method, converge at n^-1/2

Output:

N^-1/2 – consistent estimator: means that the distribution of the estimator converges in probability to the true estimator with rate n^-1/2.

The original data generalization process does not need to be a partial linear model in this more generalized proof!

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What is left?

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What problems do DML solve?

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Deep Learning Based Causal Inference for Large-Scale Combinatorial Experiments: Theory and Empirical Evidence

Zikun Ye, Zhiqi Zhang, Dennis J. Zhang, Heng Zhang, Renyu Zhang
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Outline of the Talk

Introduction: Motivation Example and Potential Solutions

Theory: Debiased Deep Learning and Asymptotics

Empirics: Results with Field Experiment Implementation

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A/B Tests are Common Practice for Online Platforms

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Multiple A/B Tests on TikTok

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Multiple A/B Tests on TikTok

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Multiple A/B Tests on TikTok

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Solution 1: Linear Addition

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Solution 2: Full Factorial Design

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Research Questions

Without observing outcomes of all treatment combinations:

Average Treatment Effects

How to estimate and infer the average treatment effect of any treatment combination?

Best Treatment Identification

How to identify the optimal treatment combination with the highest effect?

With minimum changes of the current experimentation platforms

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Our Solution and Contributions

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Related Literature

Double/de-biased machine learning (DML)

Correct the bias of ML estimators through Neyman orthogonal score functions + cross-fitting

Newey (1994), Chernozhukov et al. (2018, 2022), Farrell et al. (2020, 2021), Athey et al. (2018), Ellickson et al. (2022), Fan et al. (2022), Gordon et al. (2022) etc.

Valid estimation and inference with multiple experiments

Azevedo et al. (2020), Dasgupta et al. (2015), Athey et al. (2021), Pashley and Bind (2019), etc.

(Conjoint Analysis, Green and Rao 1971)

Experiments on online platforms

Evaluating and optimizing the strategies of a large-scale online platform.

Ye et al. (2022), Zeng et al. (2022), Zhang et al. (2020), Cui et al. (2019, 2020), Feldman et al. (2021), Schwartz et al. (2017), Bojinov et al. (2023), Abadie and Zhao (2023) etc.

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Outline of the Talk

Introduction: Motivation Example and Potential Solutions

Theory: Debiased Deep Learning and Asymptotics

Empirics: Results with Field Experiment Implementation

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Deep Learning Framework: Setup

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Goals and Two-stage Method

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First stage: Choice of Link Function

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How restrictive is this G function?

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How restrictive is this G function?

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First stage: Deep Learning

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First stage: Convergence

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Observability and Overlapping Conditions

We need to observe at least (m+2) conditions or (m+1) treatment conditions:

There are m+2 parameters to be estimated

Why do we choose m+2?

In practice, people typically run single experiment + joint holdout experiment, which gives us m+2 conditions including control conditions

Overlapping conditions:

All treatment conditions must be linked to each other through some path.

For example, if m = 3,

We observe (1,0,0), (1,0,1), (0,1,0). Then we cannot run our analysis since the second treatment condition does not link with any other treatment condition.

However, if we observe (0,1,1) instead of (0,1,0), now the second treatment condition is linked to third one through (0,1,1) and the third one is linked to the first one through (1,0,1).

There is a nice graphical representation of the overlapping conditions

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Second stage: Naïve Approach

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Second stage: Neyman Orthogonality

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Intuition behind Neyman Orthogonality

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Second stage: Final Estimator

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Outline of the Talk

Introduction: Motivation Example and Potential Solutions

Theory: Debiased Deep Learning and Asymptotics

Empirics: Results with Field Experiment Implementation

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Field Experiments Setting

We collaborate with one of the top three short-video sharing platforms in the world

300M+

Daily Active Users

500M+

Monthly Active Users

$ 20M+

Ad Revenue per day

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Field Experiments Setting

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Randomization Check

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Ground-Truth ATE

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Structured DNN

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Benchmarks

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Main Result I

DeDL outperforms all benchmarks

A *first empirical validation of DML-type estimator in practice

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DeDL Outperforms All Benchmarks

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Main Result II

Parametric link function reduces prediction accuracy

De-Bias via Neyman orthogonality

increases ATE estimation accuracy

The benefit of (b) outweights the cost of (a)

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Benefit of Neyman Orthogonality

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Main Result III

DeDL only *works* when first-stage DNN converges

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MAPE Comparison with DNN Training Epoch

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Take-away

DeDL framework provides an estimator with provable theoretical guarantees and good empirical performance for analyzing multiple experiments.

DML-type estimator works very well in practice with real experiment data (in contrast to Gordon et al. (2022))

The framework is currently utilized by the platform.

We are trying to open source the framework and you can find preliminary code here:

https://github.com/zikunye2/deep_learning_based_causal_inference_for_combinatorial_experiments

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Personalized Policy Learning through Discrete Experimentation: Theory and Empirical Evidence

Zhiqi Zhang (WashU), Zhiyu Zeng (SJTU), Ruohan Zhan (UCL), Dennis Zhang (WashU)
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Platforms Encounter Strategic Decisions Involving Continuous Variables

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Imagine you are the manager of the video boosting task team…

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Industry Practice: Use Discrete Experiments for Continuous Treatments

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Limitation 1: Discrete Treatment May Not Be The Optimal

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Limitation 2: Optimal Treatment May Be Heterogeneous

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Research Question

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Outline of the Talk

Solution Illustration and Contributions

Deep Learning for Policy Targeting Framework

Validation with a Large-Scale Field Experiment

Preview

Theory

Empirics

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Outline of the Talk

Solution Illustration and Contributions

Deep Learning for Policy Targeting Framework

Validation with a Large-Scale Field Experiment

Preview

Theory

Empirics

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Solution Preview: DLPT Framework

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Solution Preview: DLPT Framework

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Contributions

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Related Literature

Personalized Pricing and Targeting: Leverage on observational/experimental data.

Lu, H., Simester, D., & Zhu, Y. (2025), Yang, J., Eckles, D., Dhillon, P., & Aral, S. (2024), Dubé, J. P., & Misra, S. (2023), Daljord, Ø. et al. (2023), Simester, D., Timoshenko, A., & Zoumpoulis, S. I. (2020),

Experiments on online platforms: Evaluating and optimizing the strategies of a large-scale online platform.

Urban, G. L., Liberali, G., MacDonald, E., Bordley, R., & Hauser, J. R. (2014), Ye et al. (2022), Zeng et al. (2022), Zhang et al. (2020), Feldman et al. (2021), Tucker C. (2014), Tucker, C., & Zhang, J. (2010), etc.

Policy learning with continuous variables: Policy evaluation and optimization.

Kallus & Zhou(2018), Chernozhukov et al. (2019), Athey et al. (2018), etc.

Double/de-biased machine learning (DML): Correct the bias of a plug-in estimator through Neyman-orthogonal score functions.

Newey (1994), Chernozhukov et al. (2018, 2022), Farrell et al. (2020, 2021), Ellickson et al. (2022), Fan et al. (2022), Ye et al. (2023), etc.

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Outline of the Talk

Solution Illustration and Contributions

Deep Learning for Policy Targeting Framework

Validation with a Large-Scale Field Experiment

Preview

Theory

Empirics

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Set up: DLPT Framework

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Key Data Generation Process Assumption

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Key Data Generation Process Assumption

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Approximation Power of Polynomials

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Set Up: Goals

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DLPT: Three-Stage Method

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Stage 1: Deep Learning

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Stage 2: Policy Value Estimation (Neyman Orthogonalized Scores)

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Stage 2: Policy Value Estimation (Neyman Orthogonalized Scores)

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Stage 3: Policy Learning

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What if … Model Misspecification

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DLPT: Three-Stage Method

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Outline of the Talk

Solution Illustration and Contributions

Deep Learning for Policy Targeting Framework

Validation with a Large-Scale Field Experiment

Preview

Theory

Empirics

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Field Experiments Setting

We collaborate with one of the top three short-video sharing platforms in the world

400M+

Daily active users

735M+

Monthly active users

$2.4B+

Total profit per year

$4.9B+

Total revenue per year

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UGC Platforms Rely on Content Created by Users

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Strategies to Encourage Content Creation

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My Wallet

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Field Experiment

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Randomization Check

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Empirical Evidence: Cash Reward Incentives Increase Content Creation

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Empirical Evidence: Heterogeneous Treatment Effects

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Structured Deep Neural Network

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Benchmarks

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Goal 1: Counterfactual Treatment Evaluation

Goal 1: Counterfactual Treatment Evaluation

DLPT outperforms all benchmarks.

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Policy Value Estimation: Cross-Evaluation Strategy

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DLPT Outperforms All Benchmarks

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Implication 1: Pre-Experiment Design

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Goal 2: Personalized Policy Learning

Goal 2: Personalized Policy Learning

(1)DLPT generates the highest profit/lowest regret across policy classes.

(2)Continuous personalized policy improves profit by 6-14%.

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Personalized Policy Learning

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Policy Classes

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Profit Comparison

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Implication 2: Selection of Policy Classes

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Take-away

High-Dimensional Causal Estimation + Policy Learning

First framework to recover continuous policy values & personalized policies with high dimensional data of discrete A/B test

Strong Theoretical Guarantees with Explicit Bounds on

Approximation error

Estimation error

Policy regret

Empirical Validation

Large-scale field experiment with ~7.4m of users

Shows practical gains from continuity + personalization in real marketing decisions

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A/B Testing is Everywhere

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A/B Testing in Research

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Faster Decisions of Post-Experiment Analysis

Long Full-Factorial Design => One-time Experiments

Ye, Zikun, Zhiqi Zhang, Dennis Zhang, Heng Zhang, and Renyu Philip Zhang. "Deep-learning-based causal inference for large-scale combinatorial experiments: Theory and empirical evidence." Forthcoming at Management Science.

Finite Discrete Treatments => Continuous Decision Space

Zhiqi Zhang, Zhiyu Zeng, Ruohan Zhan, and Dennis Zhang. "Personalized Policy Learning through Discrete Experimentation: Theory and Empirical Evidence."

Empirical Data Collection => Synthetic Generation

Wang, Mengxin, Dennis J. Zhang, and Heng Zhang. "Large Language Models for Market Research: A Data-augmentation Approach."

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Prediction error: step-by-step derivation

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ML as Prediction / Optimization

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ML as Predictive Decision Making (similar to policy learning)

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ML as Optimization

ML to optimize multiple treatments (MAB-type-of paper)

ML to optimize complex MDPs in inventory:

Gijsbrechts, J., Boute, R. N., Van Mieghem, J. A., & Zhang, D. J. (2022). Can Deep Reinforcement Learning Improve Inventory Management? Performance on Lost Sales, Dual-Sourcing, and Multi-Echelon Problems. Manufacturing & Service Operations Management.

Dai, Jim G., and Mark Gluzman. "Queueing network controls via deep reinforcement learning." Stochastic Systems 12.1 (2022): 30-67.

Three stages of DRL research in OM/OR:

Vanilla ML and DRL

ML/DRL for Operations Problems with specific structures

ML/DRL for Operations Problems that select past policies (instead of actions)

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The problem of estimation and inference

Sikun Xu, Raphael Thomadsen and Dennis J. Zhang, “Winner’s Curse in Personalized Targeting: Evidence and Solutions”

If you estimate and then optimize, you are probably going to suffer from winner’s curse in evaluation

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Personalized Targeting

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Winner’s Curse

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Winner’s Curse in Targeting One Segment of Homogeneous Consumers

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Standard Bootstrapping Can Correct the Winner’s Curse

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Standard Bootstrapping Can Correct the Winner’s Curse

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Nonsmoothness Slows Down Convergence

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Bootstrapping Outperforms Other Proposed Solutions

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ML as Structural Model Methods

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ML for Structural Estimation

Static structural model (BLP, static games, games on networks, etc.)

Core problems:

Subject to functional assumptions

Slow estimation due to numerical integration

Dynamic structural models (Russ, dynamic games, etc)

Core problems:

Cannot handle large data due to slow estimation and optimization

Subject to very strong functional-form assumptions

Dynamic game models are very restrictive on game structures

Counterfactuals are limited by optimization power

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ML as Subjects

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ML as Subjects – Human and AI Collaboration

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However, many things are still handled by human with algorithms’ help

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Human and AI Collaboration

Human and AI Collaboration are important:

In the past, psychology (or behavioral economics) as well as algorithms have been heavily studied, but not the intersection

This topic has huge potential in practice

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Human and AI Collaboration in a Process

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Research Questions

How to improve human and AI collaboration when humans are recipients of algorithmic decisions?

The Impact of Algorithm-based Work Assignment on Fairness Perceptions and Productivity: Evidence from a Field Experiment, M&SOM.

How to improve human and AI collaboration when humans are users of algorithms?

The Impact of Forced Intervention on AI Adoption, major revision, M&SOM.

How to improve algorithm design with human collaboration data?

Predicting Human Discretion to Adjust Algorithmic Prescriptions: A Large-Scale Field Experiment in Warehouse Operations, Management Science.

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ML as Subjects

ML Fairness and Discrimination: https://fairmlbook.org/

Fairness Definitions and Impossibility Results

Test Fairness in AI

Fix Fairness issues in AI

ML and Labor Economics

Eloundou, Tyna, et al. "GPTs are GPTs: An Early Look at the Labor Market Impact Potential of Large Language Models." arXiv preprint arXiv:2303.10130 (2023).

Acemoglu, Daron, and Pascual Restrepo. "Tasks, automation, and the rise in us wage inequality." Econometrica 90.5 (2022): 1973-2016.

Data Privacy

Transparency in AI

Privacy and Business outcomes:

Goldfarb, Avi, and Catherine E. Tucker. "Privacy regulation and online advertising." Management science 57, no. 1 (2011): 57-71.

Data and ML in IO: Data is now an input into the production and consumption function, which can be priced, traded and incorporated into decisions

Any equilibrium involving algorithms, Data, and other features distinct to AI.

Asker, John, Chaim Fershtman, and Ariel Pakes. "Artificial Intelligence, Algorithm Design and Pricing." In AEA Papers and Proceedings, vol. 112, pp. 452-56. American Economic Association, 2022.

ML as a species: Whether human is only part of the civilization of intelligence?

Butlin, Patrick, et al. "Consciousness in Artificial Intelligence: Insights from the Science of Consciousness." arXiv preprint arXiv:2308.08708 (2023).

Hendrycks, Dan. "Natural selection favors ais over humans." arXiv preprint arXiv:2303.16200 (2023).

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ML as Subjects

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