# Difference between revisions of "Measuring Tools"

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− | Given a target data set, whether compiled using the [[#2-Shot Method]] or [[#OnTarget]], | + | Given a target data set, whether compiled using the [[#2-Shot Method]] or [[#OnTarget]], [[Closed Form Precision]] analysis can be performed using standard spreadsheet functions. See, for example [[Media:CCI 40gr HV 100yd.xlsx]] or any of the other workbooks linked in the [[:Category:Examples|Examples]]. |

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+ | [[Media:RangeStatisticEstimation.xls]] is spreadsheet for calculating the statistical significance of [[Range Statistics]] estimates. |

## Revision as of 16:55, 26 February 2014

Tools and practical methods for measuring and analyzing precision.

# 2-Shot Method

Brent Danielson described a no-frills method for accumulating arbitrarily large shot sample sets for statistical analysis: Since our statistics all depend on the sample radius:

- Shoot two shots at a single aim point
- Measure their center-to-center distance. This produces two radius sample points, both equal to half the measured distance.
- Repeat this process until satisfied with the quantity of data points.

Calculation of sigma from Danielson's sample data, as well as hypothesis analysis, are shown in Media:DanielsonExample.xlsx.

# OnTarget

Jeffrey Block's OnTarget Precision Calculator is the most convenient package for converting a target image into data points for analysis. It accounts for scale and distance and automatically calculates Mean Radius (called "Average to Center" in the software) and Extreme Spread (called "Max Spread").

The more expensive Target Data System can automatically identify and aggregate shots on scans of its specially-coded targets.

# shotGroups Analysis Package

Daniel Wollschlaeger built the shotGroups package for the open-source statistical environment R. It provides functions to analyze target groups with respect to their shape, location (accuracy) and spread (precision). The package works with point data exported from OnTarget and also includes functions to plot the group with precision indicators like the bounding box, maximum spread or minimum covering circle.

To get started:

- Install R from http://cran.fhcrc.org/ (direct link to download directory for the Windows version)
- Install RStudio from http://www.rstudio.com/ide/download/desktop
- For a first introduction to R, see http://tryr.codeschool.com/ or http://www.statmethods.net/
- Open RStudio, and in the console window
- Run
`install.packages("shotGroups")`

to download the latest version of**shotGroups**with all dependencies. - Now run
`library(shotGroups) # load the package`

- Now you can run the examples. In RStudio all output diagrams will be displayed in the Plots tab:
`example(groupSpread)`

`example(groupLocation)`

`example(groupShape)`

- Run

For more, see the package description, the complete manual for all functions, or run `help(package="shotGroups")`

# Spreadsheet Analysis

Given a target data set, whether compiled using the #2-Shot Method or #OnTarget, Closed Form Precision analysis can be performed using standard spreadsheet functions. See, for example Media:CCI 40gr HV 100yd.xlsx or any of the other workbooks linked in the Examples.

Media:RangeStatisticEstimation.xls is spreadsheet for calculating the statistical significance of Range Statistics estimates.