European "group size" calculation method?

[BigFatGuy]

Americans tend to judge groups by the worst spread in any one direction: "about a 4" group at x yards..."

I read somewhere that the Europeans have a different method (at least in military trials) involving using statistical methods to calculate the "center of mass" of a group, and then items such as the standard deviation.

I cannot find any real documentation of this method online... I can't even find a name for the method.

Can anyone give me a good reference, or phrase to google?

Thanks!

[God Bless America]

C.E.P. it's the circular error probable or something like that.

Get the range buddy app and it calculates mean radius among other values.

ETA: http://ballistipedia.com/index.php?t...bing_Precision

[BigFatGuy]

good man!

Thank you!

[sbo80]

CEP is really a predictor statistic not a historical measurement. And it doesn't really work for a small sample size of 3 or 5 like a shot group. "CEP90" means 90% of shots will fall within a specific radius and is a typical measurement called out. CEP50 is 50%, and would be a smaller number. Same kind of statistic is used for bombs and artillery too, but it's based on thousands of data points. CEP90 for a bomb might be 10 meters, but CEP50 is like 3 meters. Above 90 the probability is usually huge to account for some fault or error/defect, so you'd get CEP99.7 is like 150 meters. It's a stat that might be used for a barrel manufacturer I suppose. Instead of saying "garuanteed 1 MOA accuracy" they could more technically say "CEP90 is 1 MOA."