Glossary of Terms

All complex subjects have their own terminology that sometimes makes it hard for new people to break into the field. This sometimes includes uncommon words, but more often than not a subject will have very specific meanings for common words - the discussion of errors vs mistakes in this video is a good example of this.

This glossary is a reference of some of the uncommon terms and specific definitions of more common words that you will encounter throughout Data Tree and your broader dealings with data. 

Many of these definitions come from the course materials and experts that helped develop Data Tree. Others come from the CASRAI Dictionary. Those definitions are kindly made available under a Creative Commons Attribution 4.0 International License.

Browse the glossary using this index

Special | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | ALL



The variance is a measure of variability, and is often denoted by s2. In simple statistical methods the square root of the variance, s, which is called the standard deviation, is often used more. The standard deviation has the same units as the data themselves and is therefore easier to interpret. The variance becomes more useful in its own right when the contribution of different sources of variation are being assessed. This leads to a presentation called the “analysis of variance”, often written as ANOVA.

Version control

Control over time of data, computer code, software, and documents that allows for the ability to revert to a previous revision, which is critical for data traceability, tracking edits, and correcting mistakes. Version control generates a (changed) copy of a data object that is uniquely labeled with a version number. The intent is to track changes to a data object, by making versioned copies. Note that a version is different from a backup copy, which is typically a copy made at a specific point in time, or a replica. 

- CASRAI Dictionary

Version control is very popular in programming, and many coders use Git or Subversion to track changes to their scripts  and other text-based files. Other, simpler version control systems include things like MS Word's "track changes" feature, and the feature that many cloud storage facilities such as Dropbox and Google Drive have that allows users to revert to previous versions of documents stored in their systems for limited periods.


Representing data visually to enable understanding of its significance; to highlight patterns and trends that might otherwise be missed; to communicate data quickly and in a meaningful way.