2-SHOT GROUP SURPRISE

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  • Last Post 13 September 2018
joeb33050 posted this 12 September 2018

 

SHOTS PER GROUP

 

Here, accuracy = group size = the distance between the two furthest-apart hole centers.

 

Here, a “load” is every element of the shooting.

 

When we shoot groups to estimate the long-term-accuracy of a load, there is a precision of that estimate. That precision is expressed, (example), thus: “Based on the test, we are 95% sure that the long-term-accuracy of the load is .94” +/- 14%”.

 

We see 10 or 5 or 3 shot groups reported; and advocates staunchly defending their choice of shots per group.

 

After analysis, I find that there is no practical difference between estimate precision and the number of shots per group.

 

Shots per group doesn’t matter.

 

The total number of shots fired in a test does matter; a lot.

 

 

 

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Larry Gibson posted this 12 September 2018

So, then, what is your conclusion/recommendation of the total number of shots needed to achieve a 95% surety?

LMG

Concealment is not cover.........

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joeb33050 posted this 13 September 2018

So, then, what is your conclusion/recommendation of the total number of shots needed to achieve a 95% surety?

LMG

This is the form of conclusions that can be made3:

“Based on the test, we are 95% sure that the long-term-accuracy of the load is some” +/- some%”.

My recipe is 5, 5-shot groups, the NRA also.

(I shoot either 50 or 75 shots in 5- shot groups each trip to the range.. I am much more comfortable with 50; 75 allows a look at 3 loads.)

5, 5-shot groups, 25 shots:“Based on the test, we are 95% sure that the long-term-accuracy of the load is the test average”, +/- 38%”.

10, 5-shot groups, 50 shots: “Based on the test, we are 95% sure that the long-term-accuracy of the load is the test average”, +/- 27%”.

20, 5-shot groups, 100 shots: “Based on the test, we are 95% sure that the long-term-accuracy of the load is the test average”, +/- 19%”.

50, 5-shot groups, 250 shots: “Based on the test, we are 95% sure that the long-term-accuracy of the load is the test average”, +/- 12%”.

5, 10-shot groups, 50 shots: “Based on the test, we are 95% sure that the long-term-accuracy of the load is the

the test average”, +/- 30%”.

25, 2-shot groups, 50 shots: “Based on the test, we are 95% sure that the long-term-accuracy of the load is the test average”, +/- 29%”.

 

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