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Sense and Selection

The following essay is by Chaste. The article was written in early 2018. ——— I will discuss the confounding selection strategies of England, India, and South Africa in the recently finished series. I won’t talk about minutiae like whether Vince’s technique is suited to Australian conditions or whether Rohit

Subscribing To Unpopular Opinion

How does the move from advertising-supported content to a subscription model, e.g., NY Times, Substack luminaries, etc., change the content being produced? Ben Thompson mulls over the question in a new column. One of the changes he foresees is that the content will be increasingly geared toward subscribers—elites

Too Much Churn: Estimating Customer Churn

A new paper uses financial transaction data to estimate customer churn in consumer-facing companies. The paper defines churn as follows: There are three concerns with the definition: 1. The definition doesn’t make clear what is the normalizing constant for calculating the share. Given that the value “can vary between

94.5% Certain That Covid Vaccine Will Be Less Than 94.5% Effective

“On Sunday, an independent monitoring board broke the code to examine 95 infections that were recorded starting two weeks after volunteers’ second dose — and discovered all but five illnesses occurred in participants who got the placebo.” Moderna Says Its COVID-19 Vaccine Is 94.5% Effective In Early Tests The data

Fat Or Not: Toward 'Proper Training of DL Models'

A new paper introduces a DL model to enable ‘computer aided diagnosis of obesity.’ Some concerns: 1. Better baselines: BMI is easy to calculate and it would be useful to compare the results to BMI. 2. Incorrect statement: The authors write: “the data partition in all the image sets are

Not So Robust: The Limitations of "Doubly Robust" ATE Estimators

Doubly Robust (DR) estimators of ATE are all the rage. One popular DR estimator is Robins’ Augmented IPW (AIPW). The reason why Robins’ AIPW estimator is called doubly robust is that if either your IPW model or your y ~ x model is correctly specified, you get ATE. Great! Calling something

Instrumental Music: When It Rains, It Pours

In a new paper, Jon Mellon reviews 185 papers that use weather as an instrument and finds that researchers have linked 137 variables to weather. You can read it as each paper needing to contend with 136 violations of the exclusion restriction, but the situation is likely less dire. For

What’s the Next Best Thing to Learn?

With Gaurav Gandhi Recommendation engines are everywhere. These systems recommend what shows to watch on Netflix and what products to buy on Amazon. Since at least the Netflix Prize, the conventional wisdom is that recommendation engines have become very good. Except that they are not. Some of the deficiencies are

Unmatched: The Problem With Comparing Matching Methods

In many matching papers, the key claim proceeds as follows: our matching method is better than others because on this set of contrived data, treatment effect estimates are closest to those from the ‘gold standard’ (experimental evidence). Let’s side-step concerns related to an important point: evidence that a method