Prediction calibration
Compare stated probabilities with recorded outcomes. A confident wrong prediction contributes more error than a cautious one; a few events are not enough to establish forecasting skill.
Your inputs
Start with the example values, then replace them with your own. For tables, keep the vertical bar separators and use a dot for decimals.
A small or biased sample can give misleading results. This tool does not diagnose conditions or justify medical, financial or other consequential decisions.
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Result and workspace
Use the start button to open your result or activity.
How it works
Brier score = mean((probability / 100 − outcome)²). Lower scores indicate smaller probability errors on these observations.
Worked example
These sample results use the original example inputs in the form. They do not change when you edit your inputs; your own result appears in the workspace.
- Observations: 2
- Brier score: 0.365
| Event | Probability | Outcome | Squared error |
|---|---|---|---|
| Rain | 0.7 | 1 | 0.09 |
| Bus on time | 0.8 | 0 | 0.64 |
Read the result carefully
Results depend on the values and assumptions shown above. Change one input at a time to see its effect. A blank or unavailable result means the data does not support a calculation; it is not zero.