BacktestFolio · Glossary
Z-score
In plain language
A Z-score of +1.5 means that fund has a Sharpe 1.5 standard deviations above the group average — better than most peers. Z=0 is exactly average. A negative Z is below average. Looking at bubble size in the scatter is like reading Z-scores at a glance.
Technical definition
Standardised measure indicating how many standard deviations a value lies from the group mean: Z = (value − mean) / σ. In BacktestFolio's Risk vs Return scatter chart, the Z-score is computed on the Sharpe ratio of the funds in the group and determines bubble size.