Thread: Testing a conventional approach to load development

Funnily enough, with these SD for each group, for an 80% power (80/100 times you test you will detect the statistically significant difference in mean group radius and reject the null hypothesis they are the same), you need at minimum 19 shot groups.

This is rather revealing when one group is 77% bigger and has a 66% larger mean radius than the other, it still takes at least 19 shots to be sure they're different, because of the quite large variance (SD) of the samples.

Just playing here:
Assuming consistent SD of group 1 = 0.38cm and SD of group 2 = 0.58. Required sample size to detect a few differences in mean radius are below.
0.1cm difference in mean radius = 379 shot groups
0.2cm = 96
0.3cm = 44
0.4cm = 25
0.5cm = 17
0.6cm = 12
0.7cm = 9
0.8cm = 8
0.9cm = 6
1.0cm = 6
1.1cm = 5
.
.
.
1.6cm = 3

Post script; nothing wrong with your stats assuming you're picking the t-test for unequal variances. It's the appropriate test.

Originally Posted by Makros

Funnily enough, with these SD for each group, for an 80% power (80/100 times you test you will detect the statistically significant difference in mean group radius and reject the null hypothesis they are the same), you need at minimum 19 shot groups.

This is rather revealing when one group is 77% bigger and has a 66% larger mean radius than the other, it still takes at least 19 shots to be sure they're different, because of the quite large variance (SD) of the samples.

Just playing here:
Assuming consistent SD of group 1 = 0.38cm and SD of group 2 = 0.58. Required sample size to detect a few differences in mean radius are below.
0.1cm difference in mean radius = 379 shot groups
0.2cm = 96
0.3cm = 44
0.4cm = 25
0.5cm = 17
0.6cm = 12
0.7cm = 9
0.8cm = 8
0.9cm = 6
1.0cm = 6
1.1cm = 5
.
.
.
1.6cm = 3

Post script; nothing wrong with your stats assuming you're picking the t-test for unequal variances. It's the appropriate test.

Brilliant insight into the realm of statistics there!
Just shows it is ridiculous for the average shooter to bother being statistically confident in their load.

This is the reason why I'll stick to my load development techniques which are only 3-5shot groups, followed by multiple (different shooting sessions) 3-5 shot groups of whatever load I think has the best potential.
If they look good and sd's are acceptable, then I'll have confidence in the load/rifle. This will lead to confident shooting which is a major factor on the hill hunting or gong shooting.