How the OCEAN Personality Trait Scale Actually Works

The OCEAN scale measures each of the five big personality traits as a continuum: there are no “extraverts” and “introverts,” just people at different points along the same line. What the five letters stand for is covered in what OCEAN means in psychology. This article is about something else: how the scale is scored and how a profile is read, which is what really matters when you have your result in front of you.

As informational content, this article offers a general overview and doesn’t replace an evaluation by a qualified professional.

From answers to raw score

It all starts with a questionnaire of statements rated on an agreement scale, usually with five points. The calculation takes two simple steps:

1. Reverse the items worded in the opposite direction. If an openness statement says “Art doesn’t interest me much,” a “Strongly agree” (5) counts as a 1. We explain why these items exist in what Big Five test questions look like.
2. Add up or average the answers for each trait. With 24 items per trait and answers from 1 to 5, a trait’s raw score ranges from 24 to 120.

That raw score, on its own, says little. An 85 in extraversion means nothing until you know what scores people in general get on that same questionnaire.

Norms: comparing you with a reference population

To interpret a score, professional questionnaires are first administered to a normative sample, a large group of people that serves as a reference. That data is used to calculate the mean and spread of each trait, and every new score is expressed relative to them.

There are two common ways to do this:

• T-scores. They transform the raw score so that the population mean is 50 and the standard deviation is 10. A T of 60 is one standard deviation above the mean; a T of 40, one below.
• Percentiles. They indicate the percentage of the reference population that scores below you. The 84th percentile means you score higher than 84% of that sample.

If the distribution is close to normal, the two scales line up like this:

T-score	Approximate percentile	Usual reading
30	2	Very low
40	16	Low
50	50	Average
60	84	High
70	98	Very high

Costa and McCrae’s NEO-PI-R manual (1992) uses bands of this kind to describe each trait and each facet. It also provides separate norms by sex and age group because, for example, women’s average agreeableness is somewhat higher than men’s (Costa, Terracciano and McCrae, 2001) and average conscientiousness increases with age (Roberts, Walton and Viechtbauer, 2006). The same raw score can be “high” for one group and “average” for another.

A sample profile, read step by step

Imagine this profile in T-scores:

Trait	T	Reading
Openness	63	High
Conscientiousness	47	Average
Extraversion	38	Low
Agreeableness	55	Average to high
Neuroticism	52	Average

Reading it isn’t about picking out the highest trait, but about seeing the combination. What emerges here is someone curious and interested in ideas, who prefers quiet settings or small groups, is warm with others and has an emotional reactivity similar to most people’s. A profile like this fits well with analytical or creative work done on one’s own, and it explains why this person can enjoy a deep conversation and be worn out by a party.

Two cautions when reading it:

• Small differences mean nothing. No questionnaire is perfectly reliable. With a reliability of 0.90, the standard error of measurement is about 3 T points, so a 52 and a 55 are, for practical purposes, the same score.
• The extremes aren’t better. A high score in conscientiousness or a low one in neuroticism isn’t a “good result,” and average scores, which are the most common, aren’t a “lack of personality.”

What our test shows (and what it doesn’t)

It’s worth being transparent about our own Big Five test. The percentages you’ll see in your result are not percentiles: they show where your score falls between the minimum and maximum possible on each trait. A 70% in openness means your answers sit closer to the high end of the scale, not that you score higher than 70% of the population.

We don’t show percentiles because we don’t have a representative normative sample, and presenting a percentile without one would mean inventing a comparison. For an assessment with population norms, you need professional instruments such as the NEO-PI-R, administered and interpreted by a professional.

How much a profile changes over the years

Traits are fairly stable, but not fixed. The meta-analysis by Roberts, Walton and Viechtbauer (2006), covering 92 longitudinal samples, found that most people gain in conscientiousness and emotional stability during young adulthood, between 20 and 40, and in agreeableness during middle and later adulthood.

This has a practical consequence for reading a profile: if you retake the test in ten years, you can expect your raw scores to shift somewhat, even though your position relative to people your age will change much less.

Sources

• Costa, P. T., & McCrae, R. R. (1992). Revised NEO Personality Inventory (NEO-PI-R) and NEO Five-Factor Inventory (NEO-FFI) professional manual. Psychological Assessment Resources.
• Costa, P. T., Terracciano, A., & McCrae, R. R. (2001). Gender differences in personality traits across cultures: Robust and surprising findings. Journal of Personality and Social Psychology, 81(2), 322-331. https://doi.org/10.1037/0022-3514.81.2.322
• Roberts, B. W., Walton, K. E., & Viechtbauer, W. (2006). Patterns of mean-level change in personality traits across the life course: A meta-analysis of longitudinal studies. Psychological Bulletin, 132(1), 1-25. https://doi.org/10.1037/0033-2909.132.1.1