An interactive on variation

Can chance make you a killer?

One hundred hospitals. One hundred operations each. Every patient has the same chance of dying. Recalculate and watch random variation label hospitals "unacceptable" — even though every hospital is identical.

5%
Number of deaths
H Acceptable hospitals
H Unacceptable hospitals
H Your hospital
Recalculate a few times and watch your own hospital drift in and out of the "unacceptable" zone. Nothing changed. Same rate, same surgeries. The labels are chasing noise.

Your hospital across 24 periods

A Process Behavior Chart of your hospital over time, using Wheeler's XmR method. Points inside the limits reflect routine variation — the system doing what it does. A point outside the limits is a signal to investigate, not proof that something changed.

Press "Run 24 periods" to build your Process Behavior Chart.

Based on the BBC's original "Can chance make you a killer?" simulation, reconstructed to teach the same lesson: a stable, predictable system will routinely produce period-to-period swings that look like performance differences. Without Process Behavior Charts, leaders reward and punish luck.

Learn more about understanding variation in healthcare metrics and Measures of Success.