Difference between revisions of "Glossary"
(Created page with "; Accuracy : Of a gun: The distance between the point of aim and point of bullet impact. Smaller differences reflect greater accuracy. See What is Precision?#Precision vs ...") |
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; Dispersion | ; Dispersion | ||
− | : | + | : A term to denote that shots are spread around the ''Center of Impact'' (CoI) without regard to any particular statistical model or measure. Shot groups that have a small spread around the CoI have low dispersion, and shots groups that have a large spread around the CoI have a high dispersion. Thus high precision implies low dispersion. In this mathematical sense precision and dispersion are inversely related. |
; Estimator | ; Estimator | ||
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: Center-to-center distances between the two widest shots on a sample target. Because it is measured from center points it is independent of the caliber of the projectile. In practice this measurement is typically produced from the outside edge of projectile holes in a target and then the projectile caliber is subtracted. | : Center-to-center distances between the two widest shots on a sample target. Because it is measured from center points it is independent of the caliber of the projectile. In practice this measurement is typically produced from the outside edge of projectile holes in a target and then the projectile caliber is subtracted. | ||
− | ; | + | ; h |
: The horizontal dimension of a target. Typically synonymous with the ''X'' axis. | : The horizontal dimension of a target. Typically synonymous with the ''X'' axis. | ||
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; Precision | ; Precision | ||
− | : | + | : A term to denote how shots are spread around the ''Center of Impact'' (CoI), generally in reference to a particular statistical model or measure. Shot groups that have a small spread around the CoI have high precision, and shots groups that have a large spread around the CoI have a low precision. Thus low precision implies high dispersion. In this mathematical sense precision and dispersion are inversely related. |
; [http://en.wikipedia.org/wiki/Rayleigh_distribution Rayleigh Distribution] | ; [http://en.wikipedia.org/wiki/Rayleigh_distribution Rayleigh Distribution] | ||
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: Angular measure defined as one inch at a hundred yards. | : Angular measure defined as one inch at a hundred yards. | ||
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: The vertical dimension of a target. Typically synonymous with the ''Y'' axis. | : The vertical dimension of a target. Typically synonymous with the ''Y'' axis. |
Revision as of 17:16, 23 May 2015
- Accuracy
- Of a gun: The distance between the point of aim and point of bullet impact. Smaller differences reflect greater accuracy. See What is Precision?#Precision vs Accuracy
- Colloquially interchanged with Precision.
- Circular Error Probable (CEP)
- CEP(p), for p ∈ [0, 1), is the radius of the smallest circle that covers proportion p of the shot group. When p is not indicated it is assumed to be 50%, so by default CEP is the median shot radius.
- Confidence Interval
- A range about an Estimate associated with a Confidence Level K. The correct way to read these values is to say, "If we repeatedly computed this Estimate using this same sampling method, we would expect the Estimate to fall within the Confidence Interval K% of the time." Therefore, the smaller the Confidence Interval the closer our Estimate is likely to be to the true value.
- Confidence Level K
- The probability associated with a Confidence Interval. K ∈ (0, 1), and we expect that in n' estimates n / K' will fall within the Confidence Interval.
- Dispersion
- A term to denote that shots are spread around the Center of Impact (CoI) without regard to any particular statistical model or measure. Shot groups that have a small spread around the CoI have low dispersion, and shots groups that have a large spread around the CoI have a high dispersion. Thus high precision implies low dispersion. In this mathematical sense precision and dispersion are inversely related.
- Estimator
- A formula or algorithm for estimating the true value of population parameter from samples of the population
- Extreme Spread
- When discussing precision, and throughout this site, this refers to Group Size, a Range Statistic defined as the maximum distance between any two shots on a target.
- In shooting sports it can also refer to the difference between the highest and lowest value recorded for muzzle velocity.
- Gaussian Distribution
- Synonym for Normal Distribution
- Group size
- Center-to-center distances between the two widest shots on a sample target. Because it is measured from center points it is independent of the caliber of the projectile. In practice this measurement is typically produced from the outside edge of projectile holes in a target and then the projectile caliber is subtracted.
- h
- The horizontal dimension of a target. Typically synonymous with the X axis.
- Mean
- The mean of a set of values \(\lbrace x \rbrace\) is also called "x-bar" and defined as \(\bar{x} \equiv \sum_{}^n x_i / n\).
- Mean Diameter (MD)
- Twice the Mean Radius
- Mean Radius (MR)
- Mean value of the Radius of shots on target.
- Minute of Angle (MOA)
- Synonym for Minute of Arc, i.e., one arc minute
- Mil
- One thousandth.
- Milliradian, a.k.a. mrad or milrad
- Radius (r)
- Here this almost always refers to the distance of a shot on target from the center, or sample center, of a target group.
- If the target is analyzed with polar coordinates this is just the polar radius.
- If the shots are recorded with Cartesian coordinates {x, y}, then \(r_i = \sqrt{(x_i - \bar{x})^2 + (y_i - \bar{y})^2}\)
- Precision
- A term to denote how shots are spread around the Center of Impact (CoI), generally in reference to a particular statistical model or measure. Shot groups that have a small spread around the CoI have high precision, and shots groups that have a large spread around the CoI have a low precision. Thus low precision implies high dispersion. In this mathematical sense precision and dispersion are inversely related.
- \(s^2\)
- Unbiased sample variance
- Sigma (σ)
- Standard Deviation (true value of the population, as opposed to a sample)
- Also the parameter for the Rayleigh Distribution, and hence for Closed Form Precision
- Sigma-hat (\(\hat{\sigma}\))
- An estimate of Sigma (σ)
- Shooter's MOA (SMOA)
- Angular measure defined as one inch at a hundred yards.
- v
- The vertical dimension of a target. Typically synonymous with the Y axis.