3. Putting It Together

Anyway, let’s revisit our targets, Figure C-1, and see if we can make some observations on error sources and type.

Figure C-1
Accuracy and Precision


  • Target (a) shooter was both precise and accurate. This means the shooter has a pretty good handle on all the errors.
  • Target (b) indicates the presence of a systematic error: shots are consistently low and left. To compensate, the shooter can either adjust the gun sights (mechanical) or aim high and right (procedural).
  • Target (c) most likely results from a minimal experience shooter (error source: personal). On average the shooter has accurate results, but it’s achieved inefficiently. As the shooter gains experience, the efficiency increases and the pattern should begin to look more like (a).
  • Target (d) can result from all sorts of error sources and types: inexperienced shooter (personal), windy conditions (natural), gun sights off (instrumental), throw in a possible mistake or two, and so on.

Because random errors are small and tend to cancel with repeated measurements we analyze them statistically. This is where we encounter terms like “standard deviation”, “95% confidence interval”, “least squares”, etc. We’ll look at basic analysis in Chapter F.

4. Equipment

In subsequent topics, equiipment use and measuring methods will be described. Included in each is a chapter on error source and behavior