Glossary
The vocabulary used across this site.
- Cronbach’s alpha
- How consistently the items on a scale agree with each other, from 0 to 1. Roughly .70 and up is usually considered adequate. Short scales have lower alpha because they have fewer items, not because they measure worse things.
- Domain
- One of the broad traits — Extraversion, Agreeableness and so on. Five of them in most models here, six in the HEXACO.
- Facet
- A narrower component of a domain. Conscientiousness contains Orderliness and Achievement-Striving, among others. Two people can share a domain score and differ sharply underneath it. The shorter inventories have no facets at all.
- Inventory
- A set of items measuring one or more traits, answered about yourself, with no correct answers. This site offers 6. A test, by contrast, has correct answers and you try to do well on it — why the distinction matters.
- Item
- One statement you rate. IPIP items are phrases rather than sentences by design — each completes an implied “I …”.
- Keyed / reverse-keyed
- Whether agreeing with an item counts toward the trait or against it. “Keep things tidy” and “Leave a mess in my room” both measure Orderliness, in opposite directions. Reverse-keyed items are flipped when scored, which is how an inventory detects someone agreeing with everything.
- Level
- The words low, average and high, cut at the 30th and 70th percentiles. Bands of a distribution, not kinds of person.
- Norms & reference group
- A table of how a named population scored, and the slice of it you are being ranked against. Every percentile on this site is relative to one.
- Percentile
- The share of that reference group scoring at or below you. A comparison, not a measurement — change the group and it changes.
- Prorating
- Scaling a partly-answered scale up to full length so it stays comparable. Used only when at least 80% of its items were answered.
- Public domain
- Free of copyright, usable by anyone for any purpose. Every personality item on this site is public domain, which is unusual — most well-known personality instruments are commercial products with licence fees. The MFQ-2's items are not public domain but openly licensed: free to use with credit to their authors.
- Raw score
- The sum of your keyed answers on a scale. This is the measurement. It never changes with who you are compared against.
- Scale
- Any group of items summed into one score. Both domains and facets are scales; so is the response scale you answer on, which is an unrelated use of the same word.
- Self-selected sample
- A group that chose to take part rather than being sampled at random. Every reference population here is one, which is the single most important caveat on this site.
- T-score
- The same comparison on a different ruler: mean 50, standard deviation 10. A T-score of 60 is one standard deviation above the group average.