I recently bought AB Analytics and I'm a bit confused about the following passage, or rather the assumptions about the uncertainties of a measurement and how AB Analytics builds the Bell curve.
“ 1 Uncertainties represent the 95% confidence intervals assuming a normal distribution. In other words, if the uncertainty in range is cited as +/- 1 meter, it means the standard deviation of range error is 0.5 meters. The simulation will model a bell curve of range error with 67% of the estimates being within +/- 0.5 meters (+/- 1σ) and 95% of the estimates being within +/- 1.0 meters (+/- 2σ). “
For example, if the measure of a distance is 800 meters +/- 1.0 meters does it mean that we can have 799 as 801 so the standard deviation is 1, why AB Analytics considers 0.5 meters?
The 67% or (+/- 1σ) could be 1 not 0.5 and the 95% (+/- 2σ) could be 2 meters non 1.
I’m thinking right or I’m doing something wrong ?
about the software is nice and very close to other software, one thing to improve is to have the possibility to edit input for metric also if you use sight in and wez simulation, in this case no way to change it, if you choose metric the possibility to input data is only in imperial and the output also.
Searching on the web about WEZ I found this what do you think about it ? And in any case what input you put in rifle precision ?
www.longrangeonly.com
“
Rifle Precision (ES). To use WEZ software correctly, your measured group size must be corrected to get the Rifle Precision extreme spread (ES) input value in MOA. The procedure for correcting extreme spread values is not explained in AB Analytics. Relying on the guidance given in the software documentation alone, the reader can easily be misled. One issue is that AB Analytics uses bivariate (two separate distributions) statistics for dispersion. That means that there are separate distributions for vertical and horizontal dispersion. However, the WEZ software uses only one input parameter for group size: Rifle Precision. To make matters worse, most software for calculating the standard deviation of dispersion assumes a single variable distribution, not two variables. Also, WEZ software defines Rifle Precision to be 4 times the standard deviation.
In AB Analytics, a value of Rifle Precision =1 MOA, produces P(hit) = 68% for a +/-0.25 MOA vertical stripe (all system variables being set to zero). That result confirms that the distribution is bivariate, and it means that you should multiply a bivariate standard deviation value by 4 to get the Rifle Precision input value for WEZ software. Unfortunately, most shooters don’t measure or calculate the bivariate standard deviation. They typically measure extreme spread for a group of 3-10 shots.
[Note: page 61 of Accuracy and Precision states that ‘… 95% of shots fall within a 0.5 MOA radius to produce a “1.0 MOA” group’. Unfortunately, this statement is incorrect. Due to the bivariate 4
distribution, actually only 84% of shots fall within a 0.5 MOA radius for a Rifle Precision=1.0 MOA (all system variables being set to zero).] “
“ 1 Uncertainties represent the 95% confidence intervals assuming a normal distribution. In other words, if the uncertainty in range is cited as +/- 1 meter, it means the standard deviation of range error is 0.5 meters. The simulation will model a bell curve of range error with 67% of the estimates being within +/- 0.5 meters (+/- 1σ) and 95% of the estimates being within +/- 1.0 meters (+/- 2σ). “
For example, if the measure of a distance is 800 meters +/- 1.0 meters does it mean that we can have 799 as 801 so the standard deviation is 1, why AB Analytics considers 0.5 meters?
The 67% or (+/- 1σ) could be 1 not 0.5 and the 95% (+/- 2σ) could be 2 meters non 1.
I’m thinking right or I’m doing something wrong ?
about the software is nice and very close to other software, one thing to improve is to have the possibility to edit input for metric also if you use sight in and wez simulation, in this case no way to change it, if you choose metric the possibility to input data is only in imperial and the output also.
Searching on the web about WEZ I found this what do you think about it ? And in any case what input you put in rifle precision ?
A Users Guide to Dispersion Analysis - Long Range Only
A Users Guide to Dispersion Analysis Bruce Winker High Power Optics When you’re developing a new load for a long range rifle do you ask yourself, “What group size is good enough?” “Should I strive for a 0.5″ group, or is a 1.0″ group good enough?” What about muzzle velocity? “Is 50 fps extreme...
www.longrangeonly.com
“
Rifle Precision (ES). To use WEZ software correctly, your measured group size must be corrected to get the Rifle Precision extreme spread (ES) input value in MOA. The procedure for correcting extreme spread values is not explained in AB Analytics. Relying on the guidance given in the software documentation alone, the reader can easily be misled. One issue is that AB Analytics uses bivariate (two separate distributions) statistics for dispersion. That means that there are separate distributions for vertical and horizontal dispersion. However, the WEZ software uses only one input parameter for group size: Rifle Precision. To make matters worse, most software for calculating the standard deviation of dispersion assumes a single variable distribution, not two variables. Also, WEZ software defines Rifle Precision to be 4 times the standard deviation.
In AB Analytics, a value of Rifle Precision =1 MOA, produces P(hit) = 68% for a +/-0.25 MOA vertical stripe (all system variables being set to zero). That result confirms that the distribution is bivariate, and it means that you should multiply a bivariate standard deviation value by 4 to get the Rifle Precision input value for WEZ software. Unfortunately, most shooters don’t measure or calculate the bivariate standard deviation. They typically measure extreme spread for a group of 3-10 shots.
[Note: page 61 of Accuracy and Precision states that ‘… 95% of shots fall within a 0.5 MOA radius to produce a “1.0 MOA” group’. Unfortunately, this statement is incorrect. Due to the bivariate 4
distribution, actually only 84% of shots fall within a 0.5 MOA radius for a Rifle Precision=1.0 MOA (all system variables being set to zero).] “
