Leslie, 1993, Is "Group Size" the Best Measure of Accuracy?
Is "Group Size" the Best Measure of Accuracy?, John "Jack" E. Leslie III, 1993. Notes:
- Extreme Spread: Maximum distance between any two shots in group. Note that this effectively only uses two data points.
- Figure of Merit (FOM): Average of the maximum horizontal group spread and the maximum vertical group spread. This uses only 2-4 data points depending on the group.
- Mean Radius: Average distance to center of group for all shots.
- Radial Standard Deviation: Sqrt (Horizontal Variance + Vertical Variance).
- Found military using RSD and Mean Radius as early a 1918.
Monte Carlo analysis shows sample RSD to be most accurate predictor of accuracy, followed closely by Mean Radius. I.e., they can distinguish between loads of different inherent accuracy more accurately and using fewer shots.