Range (what shooters call ES) is directly convertible to standard deviation. As stated earlier, estimates at variation based on small samples can quite far off.
Isn't that what the buttons on a calculator are for?
Been awhile ago, someone posted a factor to multiply the results of less than a ten shot groups. Do you have those numbers Denton?
Nice thing about the electronic targets people are migrating to, they give you a velocity at the target. Shot Marker also gives you a SD for your string. I haven't researched the accuracy of the numbers.
