Twelve repeatable labs

Change one assumption. Watch the conclusion move.

Each lab uses synthetic data, a visible seed, and a plain-language summary. No sign-up and no hidden score.

What "synthetic" means here

The numbers are generated inside your browser from a documented model. They do not describe actual people, products, or events.

12 items shown

LAB 01Sampling

Why averages settle down

Draw repeated samples from a right-skewed synthetic population and watch the distribution of their means change with sample size.

3 controls
LAB 02Sampling

One value, two centers

Move one synthetic observation and compare how the mean, median, and middle 80% respond.

1 controls
LAB 03Uncertainty

What 95% covers

Generate many intervals from one fixed synthetic population and count how often the method captures its known mean.

4 controls
LAB 04Uncertainty

When accurate alerts mislead

Change prevalence, sensitivity, and specificity, then inspect every expected true and false alert in a synthetic population.

4 controls
LAB 06Relationships

What correlation leaves out

Compare positive, negative, near-zero unstructured, and near-zero curved synthetic relationships to see what a linear summary cannot preserve.

2 controls
LAB 07Communication

Points are not percent

Set a baseline and a new rate, then compare percentage points, relative change, and absolute counts side by side.

3 controls
LAB 08Relationships

Why extremes drift inward

Create two noisy synthetic measurements, select the most extreme first results, and compare the same selected group on retest.

3 controls
LAB 09Sampling

When more answers miss the target

Repeat a probability sample and a tilted voluntary sample, then separate shrinking random variation from persistent selection bias.

4 controls
LAB 10Uncertainty

Why fair sequences form streaks

Generate binary sequences, count their runs, and compare independent trials with a mechanism that alternates too often.

4 controls
LAB 11Communication

The same values on two axes

Place five synthetic rates on a full and focused scale, then measure how axis limits change visible distance without changing the data.

2 controls
LAB 12Uncertainty

Twenty chances for one false alarm

Generate complete families of valid null p-values and compare an unadjusted threshold with Bonferroni family-wise control.

5 controls