econometrics.blog

Puzzles, intuitions, and sundry economic tricks.

Latest — 06 AUG 2026

Econometrics Puzzler #3: I've Got the Power

Today’s challenge is to do a power calculation in your head. No paper, no pencils, no normal tables, and no statistical software packages are allowed!

Contents

4

The puzzlers

Short problems that test econometric intuition. Read the question, think, then open the fold. Four so far.

I.

Causal inference & identification

8
A Good Instrument is a Bad Control
Part I — Why controlling for an instrument backfires 2023
Part II — The general result, with simulations 2025
Econometrics Puzzler #1: To Instrument or Not? 2025
How to Do Regression Adjustment 2024
Three Ways of Thinking About Instrumental Variables 2022
Regressions with a Mis-measured, Binary Outcome 2021
Beyond Classical Measurement Error 2021
(Mis)understanding Selection on Observables 2021
II.

Inference & uncertainty

8
Econometrics Puzzler #3: I've Got the Power 2026
Overlapping Confidence Intervals
Part I — What overlap does and doesn't tell you 2025
Part II — Correlated estimates and the law of cosines 2025
Not Quite the James-Stein Estimator 2024
Econometrics Puzzler #0: Is it Better to Improve Sensitivity or Specificity? 2024
From the Poisson Distribution to Stirling's Approximation 2022
The Wilson Confidence Interval for a Proportion 2022
Don't Use the Textbook CI for a Proportion 2021
III.

Econometric theory

5
Two FWL Theorems for the Price of One 2025
Econometrics Puzzler #2: Fitting a Regression with Fitted Values 2025
Sims and Uhlig (1991) Replication 2024
Local Asymptotics: The Simplest Possible Example 2022
A New Way of Looking at Least Squares 2022
IV.

Teaching & explainers

7
How to Read an Econometrics Paper 2024
Random Variables Cheatsheet 2023
Why Econometrics is Confusing
Part I — The Error Term 2022
Part II — The Independence Zoo 2023
Understanding the F Statistic 2021
Untangling Cause and Effect Without Experiments 2021
Thirty isn't the magic number 2021
V.

Computing & applied work

7
Street Fighting Numerical Analysis
Part I — Floating point, or why 0.2 × 20 isn't 4 2021
Part II — Complex step differentiation 2026
The R Formula Cheatsheet 2023
Lessons from the Oxford Vaccination Survey 2021
Past the Peak? Excess Deaths in England and Wales 2020
UK Excess Deaths by Age Group and Sex 2020
Excess Deaths in England and Wales 2020
A.

Odds & ends

4
A Makeover for econometrics.blog 2026
Chris Sims - RIP 2026
The Return of econometrics.blog! 2024
Econometricians Anonymous 2021

2026

4
06 AUG Econometrics Puzzler #3: I've Got the Power 6 min
26 APR Complex Step Differentiation 7 min
09 APR A Makeover for econometrics.blog 1 min
15 MAR Chris Sims - RIP 3 min

2025

6
22 NOV Overlapping Confidence Intervals: Part II 11 min
15 NOV Overlapping Confidence Intervals 13 min
28 AUG A Good Instrument is a Bad Control: Part II 10 min
14 AUG Two FWL Theorems for the Price of One 10 min
24 JUL Econometrics Puzzler #2: Fitting a Regression with Fitted Values 3 min
13 JUL Econometrics Puzzler #1: To Instrument or Not? 7 min

2024

6
10 AUG Not Quite the James-Stein Estimator 37 min
02 AUG How to Do Regression Adjustment 24 min
25 JUL Econometrics Puzzler #0: Is it Better to Improve Sensitivity or Specificity? 9 min
20 JUL How to Read an Econometrics Paper 13 min
15 JUL Sims and Uhlig (1991) Replication 8 min
14 JUL The Return of econometrics.blog! 2 min

2023

4
29 JUN A Good Instrument is a Bad Control 9 min
19 APR The R Formula Cheatsheet 2 min
07 JAN Random Variables Cheatsheet 1 min
01 JAN Why Econometrics is Confusing Part II: The Independence Zoo 20 min

2022

6
18 NOV From the Poisson Distribution to Stirling's Approximation 7 min
12 NOV Local Asymptotics: The Simplest Possible Example 6 min
06 NOV Three Ways of Thinking About Instrumental Variables 11 min
24 JUL Why Econometrics is Confusing Part I: The Error Term 5 min
14 MAR A New Way of Looking at Least Squares 12 min
05 FEB The Wilson Confidence Interval for a Proportion 24 min

2021

10
31 DEC Lessons from the Oxford Vaccination Survey 14 min
29 OCT Street Fighting Numerical Analysis - Part I 8 min
04 OCT Don't Use the Textbook CI for a Proportion 11 min
30 AUG Regressions with a Mis-measured, Binary Outcome 16 min
23 AUG Beyond Classical Measurement Error 5 min
15 AUG Understanding the F Statistic 20 min
08 AUG (Mis)understanding Selection on Observables 6 min
01 AUG Untangling Cause and Effect Without Experiments 8 min
08 MAY Thirty isn't the magic number 15 min
01 APR Econometricians Anonymous 4 min

2020

3
13 MAY Past the Peak? Excess Deaths in England and Wales 3 min
13 MAY UK Excess Deaths by Age Group and Sex 5 min
04 MAY Excess Deaths in England and Wales 3 min

39 posts since 2020

Puzzles, intuitions, and sundry economic tricks.

Also

Econometrics Puzzler #3: I've Got the Power

Complex Step Differentiation

A Makeover for econometrics.blog

Chris Sims - RIP

Overlapping Confidence Intervals: Part II

Overlapping Confidence Intervals

A Good Instrument is a Bad Control: Part II

Two FWL Theorems for the Price of One

Econometrics Puzzler #2: Fitting a Regression with Fitted Values

Econometrics Puzzler #1: To Instrument or Not?

Not Quite the James-Stein Estimator

How to Do Regression Adjustment

Econometrics Puzzler #0: Is it Better to Improve Sensitivity or Specificity?

How to Read an Econometrics Paper

Sims and Uhlig (1991) Replication

The Return of econometrics.blog!

A Good Instrument is a Bad Control

The R Formula Cheatsheet

Random Variables Cheatsheet

Why Econometrics is Confusing Part II: The Independence Zoo

From the Poisson Distribution to Stirling's Approximation

Local Asymptotics: The Simplest Possible Example

Three Ways of Thinking About Instrumental Variables

Why Econometrics is Confusing Part I: The Error Term

A New Way of Looking at Least Squares

The Wilson Confidence Interval for a Proportion

Lessons from the Oxford Vaccination Survey

Street Fighting Numerical Analysis - Part I

Don't Use the Textbook CI for a Proportion

Regressions with a Mis-measured, Binary Outcome

Beyond Classical Measurement Error

Understanding the F Statistic

(Mis)understanding Selection on Observables

Untangling Cause and Effect Without Experiments

Thirty isn't the magic number

Econometricians Anonymous

Past the Peak? Excess Deaths in England and Wales

UK Excess Deaths by Age Group and Sex

Excess Deaths in England and Wales

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