Probably Random

Regression to the Mean in Psychology Explained

2026-11-01T12:45:57.726467-08:00

In psychology, regression to the mean usually refers to a mistake people make, not to the statistics. After an extreme result, the next one tends to land...

Confidence Interval Explained

2026-10-29T13:15:34.519796-07:00

Your A/B test dashboard says the new checkout page converts at 4.2%, with a 95% confidence interval of 3.6% to 4.8%. Does that mean there is a 95% chance...

Misleading Charts Examples and How to Spot Them

2026-10-26T12:53:54.634145-07:00

What makes a chart misleading if every number on it is correct? Usually it is the drawing, not the data. A misleading chart takes true figures and encodes...

Regression to the Mean Between Generations Explained

2026-10-23T11:19:10.513516-07:00

Regression to the mean between generations is the pattern in which unusually tall or short parents tend to have children who are still taller or shorter...

The Definition of Regression to the Mean

2026-10-20T09:19:48.685248-07:00

Regression to the mean is the tendency for an unusually high or low measurement to be followed by one closer to the average, simply because the two...

One-Tailed vs Two-Tailed Tests Explained

2026-10-16T20:14:51.156821-07:00

Use a two-tailed test unless, before any data arrives, you can say that a result in the opposite direction would lead to exactly the same decision as no...

What Is P-Hacking

2026-10-13T19:44:09.050085-07:00

P-hacking is running several analyses on the same data until one of them comes out statistically significant, usually p < .05, and then reporting that one...

Why a Bigger Sample Shrinks Your P-Value

2026-10-10T18:17:15.843577-07:00

Why does the same small lift look like noise in a small test and a sure thing in a big one? Because a p-value depends on two things, not one. It reflects...

What Counts as a Good P-Value

2026-10-07T17:36:10.804418-07:00

There is no single good p-value. What counts as "good enough" depends on your field and on what a false alarm would cost you. The conventions run from 0.10...

P-Value vs Confidence Interval

2026-10-04T14:16:57.137006-07:00

If you have both a p-value and a confidence interval for the same result, read the interval first. The two come from the same arithmetic, so a 95%...

Why 0.05 Is the Standard P-Value Cutoff

2026-10-01T13:14:57.316825-07:00

Why is the p-value cutoff 0.05? Ronald Fisher, a British statistician, called it convenient in a 1925 textbook, and nearly everyone followed him. It is a...

How to Calculate a P-Value by Hand

2026-09-28T12:14:07.067472-07:00

When you finish, you will have a two-tailed p-value for a one-sample t-test, built from four numbers: the sample mean, the sample standard deviation, the...

Regression to the Mean, Explained With Real Numbers

2026-09-25T11:14:18.714648-07:00

Why does the sales rep who had a record month usually have an ordinary one right after? Most of the time the cause is regression to the mean: an unusually...

Election Win Probability Charts Aren't Vote Shares

2026-09-22T10:16:54.333091-07:00

When a forecast says Democrats have an 85 percent chance of winning the House, that is not a prediction that they will win 85 percent of anything. It is a...

Why 2026 Midterm Forecasts Disagree So Much About Who Wins the House

2026-09-18T19:13:25.164408-07:00

Three forecasts of the same midterm elections are live this month and they look irreconcilable. A Cornell University model presented on September 3, 2026...

How Publication Bias Kept a Fabricated Procrastination Study Famous for 24 Years

2026-09-18T19:13:25.157723-07:00

Publication bias is the tendency for a study to get published because of how its results turned out rather than how well it was done. Big, clean, surprising...

What a p-value actually tells you, and what it does not

2026-09-18T19:13:25.147584-07:00

What is a p-value? It is the probability of seeing a result at least as extreme as yours if there were no real effect, that is, if the null hypothesis were...