AMERICAN RIFLEMAN GUN TESTS

lotech,

Absolutely.  Even one five shot group of each when comparing loads may give you fairly reliable information if the difference is big enough. If one group is twice as big it is a pretty good guess (reasonable degree of confidence) that the smaller group indicated the best load. It's when the difference in group sizes is small that we may kid ourselves that we have found the better of the two even if we have shot four of five groups of each load. I tried to show this in my recent post about unlubed bullets when four groups each showed the groups with lubed bullets being 16% larger. Also see “Lube Test” in Fouling Shot #233 where I was led astray even with 5-5 shot groups with each.

As I see it the practical role of statistics to shooters isn’t to inspire them to buy a statistics book or to claim that they need dozens of groups (which is entirely impractical) when trying to find out if upping the powder charge one grain will improve accuracy. 

Instead I think the value of statistics is that it allows statisticians to produce tables like the ones Joe has given us that can help us develop a better “feel” about the PROBABILITY, or likelihood that a test is telling us the truth. That is, giving us some idea of how likely (what level of confidence) the results are right.

To make the best decisions as we struggle to improve our loads or our equipment we need to have a feel for what those probabilities are the same as a good poker or blackjack player needs to understand the appropriate probabilities. If he doesn’t he will make unnecessarily bad decisions and soon be separated from his money.

Without a feel for the probabilities associated with shooting, a shooter may make similar unforced errors. For example, if a shooter has digested the fact that in a string of 5 five shot groups that on average the largest will be 1.9 times the smallest (and sometimes more) he now has a “feel” for how uncertain the measurement of any one group really is.  Although he may have measured it to .01” as .87 in., He understands that .87 may be far from the real accuracy of that rifle/load/shooter combination. This understanding should prevent him from claiming he has a 1-MOE rifle or shooting a series of five shot groups each with a slightly different powder charge and deceiving himself that he has found the best charge.  He understands that he has nothing but the very weakest and most unreliable indicator of what might be a good load.