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Data Literacy

For professionals who need to understand data, statistics, and evidence without being statisticians. Each article unpacks a real case — a famous paradox, a misleading aggregate, a result that fooled experts — and the analytical mistake behind it, so you can spot it in your own work.

Series · 18 stories

Statistical paradoxes

Famous paradoxes, fallacies, and biases, each told through the real case that made it famous and the mistake it still causes in research, evaluation, and AI today.

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All articles Statistical Analysis Survey Design & Measurement Study Design Program Evaluation AI Evaluation Statistical Consulting Data Literacy

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Data LiteracyStudy Design

The Oscar Winners Who Couldn't Have Died Young

4 min read

Oscar winners outlived their peers by nearly four years, a famous 2001 study found. Most of that gap came from when the clock started.

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Data LiteracyProgram Evaluation

The Erasers That Raised Atlanta's Test Scores

4 min read

Atlanta's test scores climbed for a decade and won its superintendent a national award. Then the state started counting eraser marks.

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Data LiteracyProgram Evaluation

The Poll of 2.4 Million That Picked the Loser

5 min read

In 1936, 2.4 million people mailed back a poll that called the election for the wrong man. The problem wasn't who got a ballot. It was who sent one back.

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Data LiteracyProgram Evaluation

The Best Schools Were Small. So Were the Worst.

4 min read

Small schools topped the test-score rankings, and foundations put billions behind them. Small schools also crowded the bottom of the rankings.

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Data LiteracyAI Evaluation

The 27 Programs That Failed Together

5 min read

Twenty-seven programmers wrote the same program separately, so their bugs should have been independent. On 1,255 test cases they failed together.

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Data Literacy

The Asylum Judges Who Couldn't Say Yes Twice

5 min read

After granting one asylum case, US judges got measurably less likely to grant the next. The cases were unrelated. The gambler's fallacy wasn't.

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Data Literacy

The Serial Numbers That Counted Germany's Tanks

5 min read

Allied intelligence thought Germany built over 1,000 tanks a month. A few captured serial numbers said far fewer, and the serial numbers were right.

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Data Literacy

The Checks That Were Just Under $100,000

5 min read

A state manager wrote 23 fake checks worth nearly $2 million. None looked odd alone. Their first digits gave the game away.

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Data Literacy

The Number That Convicted an Innocent Mother

4 min read

In 1999, a jury heard that two cot deaths had a 1-in-73-million chance. That number was wrong twice over, and the second mistake is the dangerous one.

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Data Literacy

The Answer a Thousand PhDs Called Wrong

4 min read

In 1990, Marilyn vos Savant gave the correct answer to a probability puzzle. Ten thousand readers, nearly a thousand with PhDs, insisted she was wrong.

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Data Literacy

The Protective Effect That Wasn't There

4 min read

Hospital records seemed to show diabetes protecting patients from gallbladder disease. The correlation was never real — it was manufactured by the simple fact that everyone in the data had already been admitted. A case study in Berkson's Paradox, and why a sample built by selection isn't safe to read at face value.

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Data Literacy

The Tallest Parents Never Had the Tallest Children

4 min read

In 1886, Francis Galton compared thousands of parents' and children's heights and found the pattern he'd first spotted in sweet peas: every extreme pulled back toward average, generation after generation. A real case study in regression to the mean, and why picking the worst (or best) score to intervene on can make almost anything look like it worked.

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Data Literacy

The Correlation That Was Positive for States and Negative for People

4 min read

In 1950, a sociologist found that immigrants and literacy correlated positively across U.S. states and negatively across individual people — the same census, the same year, opposite signs. A real case study in the ecological fallacy, and why a group-level number can't answer a question about the people inside it.

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Data Literacy

The Survival Rates That Improved While No One Got Better

4 min read

In 1985, lung cancer survival statistics rose in every single stage of the disease — without a single patient living longer. A real case study in the Will Rogers phenomenon, and why a rising average can hide the fact that nothing actually changed.

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Data Literacy

The Data Audit Checklist to Run Before You Start Analyzing

2 min read

Most analysis problems that look like modeling problems are actually data problems nobody checked for first. A short audit up front catches most of them before they cost you time.

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Data Literacy

The Dead Salmon That Read Minds

4 min read

A dead fish, put in a brain scanner, appeared to respond to photos of people with statistically significant brain activity. It was a joke with a serious point — about what happens when you run thousands of tests at once and only report the ones that worked.

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Data Literacy

The Test Result That Fooled the Doctors

4 min read

Give a room full of physicians a positive screening test and one prevalence number, and most will badly overestimate the odds the patient is actually sick. A short primer on base-rate neglect, and why 'accurate' tests aren't the same as trustworthy results.

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Data Literacy

The Plane That Never Made It Back

4 min read

The Air Force wanted to armor the parts of returning bombers riddled with bullet holes. A statistician told them to armor the parts that had none. A short primer on survivorship bias, and why the data you don't have can matter more than the data you do.

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Data Literacy

The Bias That Disappeared When You Looked Closer

3 min read

Berkeley's 1973 admissions numbers looked like textbook discrimination against women — until anyone checked department by department. A short primer on Simpson's Paradox, and why the number you aggregate is a choice, not a neutral fact.