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


Absolute value

The absolute value is the value of a number, disregarding its sign. It is denoted by a pair of “|” signs. For example the modulus of –2.5 is |-2.5| = 2.5.


The continued, available for use, ongoing usability of a digital resource, retaining all qualities of authenticity, accuracy and functionality deemed to be essential for the purposes the digital material was created and/or acquired for. Users who have access can retrieve, manipulate, copy, and store copies on a wide range of hard drives and external devices.

- CASRAI Dictionary

Administrative data

Information collected primarily for administrative, and not research purposes. It includes profiles and curriculum vitae of researchers, the scope and impact of research projects, funding, citations, and research outcomes. This type of data is collected by government departments and other organisations for the purposes of registration, transaction and record keeping, usually during the delivery of a service. These data are also recognized as having research value.

CASRAI Dictionary

Aggregated data

Data that are expressed in a summary form (e.g., summary statistics)

CASRAI Dictionary


The bringing together of elements. Types of aggregations differ by the nature of the processes by which elements are brought together and the reason understood for aggregating or contained as a unit. Aggregations differ in the nature of relations between the member parts.

CASRAI Dictionary


A computable set of steps to achieve a desired result.

CASRAI Dictionary

Alternative hypothesis

The alternative hypothesis, H1, is a statement of what the test is set up to establish. For example if comparing average annual rainfall in El Nino and ordinary years then we could have:
  • H0,that the two means are not equal, i.e. there is a difference between the two types of year..
The conclusion from the hypothesis test is either “Reject H0 in favour of H1.” or “Do not reject H0.” If H0 is rejected then the analysis usually continues by establishing, in this case, the extent of the difference between the two types of year.

Analogue data

Data in the form of analogue materials. RELATED TERM. Analogue materials

CASRAI Dictionary

Analogue signals

Continuous electronic signals.

CASRAI Dictionary


The discovery of meaningful multidimensional patterns in data.

CASRAI Dictionary


A rule, practice, or observation that is different from what is normal or usual.

CASRAI Dictionary


A form of privacy that is not usually needed or wanted. There are occasions, however, when a user may want anonymity (for example, to report a crime). The need is sometimes met through the use of a site, called a remailer that re-posts a message from its own address, thus disguising the originator of the message. Unfortunately, many spam distributors also take advantage of remailers.

CASRAI Dictionary

Applied science

The application of existing scientific and professional knowledge to develop practical applications in a scientific field (e.g., actuarial science, agriculture, biology, chemistry, forestry, meteorology, physics, planetary and earth sciences), scientific regulation, or patent.

CASRAI Dictionary


Fundamental organization of a system embodied in its components, their relationships to each other and to the environment, and the principles guiding its design and evolution. The term is not always used in normative or prescriptive ways. In some cases, the architecture may need to be flexible and thus more of an open framework rather than being a fixed set of components and services equal to everyone.

CASRAI Dictionary


A place or collection containing static records, documents, or other materials for long-term preservation.

CASRAI Dictionary


A curation activity that ensures that data are properly selected, stored, and can be accessed, and for which logical and physical integrity are maintained over time, including security and authenticity.

CASRAI Dictionary

At-risk data

Data that are at risk of being lost. At-risk data include data that are not easily accessible, have been dispersed, have been separated from the research output object, are stored on a medium that is obsolete or at risk of deterioration, data that were not recorded in digital form, and digital data that are available but are not useable because they have been detached from supporting data, metadata, and information needed to use and interpret them intelligently.

CASRAI Dictionary


For a numeric variable the average is a loosely used term for a measure of location. It is usually taken to be the mean, but it can also denote the median, the mode, among other things.