How the test works, in plain English.

The instrument

Stille administers the IPIP-NEO-120: a 120-item Big Five personality inventory developed by John A. Johnson (Penn State University) and built on the International Personality Item Pool curated by Lewis Goldberg. Both are open-access; the test has been used in research since the late 1990s.

We drop one of the original 30 facets (O6 Liberalism) because its items are politically loaded in a US-specific way that doesn’t generalise internationally and doesn’t belong in a self-development context. That leaves 116 items, 29 facets, 5 broad domains.

• Goldberg, L. R. (1999). A broad-bandwidth, public domain, personality inventory measuring the lower-level facets of several five-factor models. Personality Psychology in Europe, 7, 7–28.
• Johnson, J. A. (2014). Measuring thirty facets of the Five Factor Model with a 120-item public domain inventory: Development of the IPIP-NEO-120. Journal of Research in Personality, 51, 78–89.

How your scores are computed

Each item is scored 1–5 (Strongly Disagree to Strongly Agree). Items written in a negative direction (e.g. “Often forget to put things back in their proper place”) are reverse-keyed before scoring. Your raw score for each facet is the mean of its four items; your domain score is the mean of its facets’ items.

Raw scores are then converted to T-scores against a normative reference sample, then to a five-band gradation (Strongly [low], Leaning [low], Balanced, Leaning [high], Strongly [high]). The band, not the T-score, is what shows up in your report; T-scores stay in the data layer because they invite over-interpretation that the instrument can’t support.

The reference sample

Stille’s norms are computed from Johnson’s (2014) released dataset of N = 619,150 respondents, published on OSF. Norm tables are stratified by sex × age band, so your score is compared to people of your sex and approximate age rather than to the population average. We independently verified our reading of the dataset by computing Cronbach’s α for all 30 facets and 5 domains, matching Johnson’s published values within 0.008.

How New Zealand adults compare

The Johnson (2014) sample is international but skews toward English-speaking Western respondents, particularly from the US. Big Five scores show small but real cross-cultural shifts. For New Zealand adults specifically, published research using shorter Big Five measures (notably the New Zealand Attitudes and Values Study) suggests that, on average:

• Extraversion: Kiwis score slightly lower than the US-skewed international average — somewhat more reserved as a population.
• Agreeableness: Kiwis score slightly higher.
• Conscientiousness, Openness, Emotional Sensitivity: roughly comparable, with no large systematic shifts.

These shifts are real but small (typically less than a fifth of a standard deviation) — usually not enough to move an individual’s band assignment. We’ve kept the international reference for v1 rather than recalibrating against a smaller NZ sample, because the practical effect on your report is negligible and the international comparison is what the published norms can defensibly support.

We’re committed to publishing Stille-specific NZ norms once we have a large-enough sample (likely once a few hundred New Zealand respondents have completed the test). Your responses help us get there.

Sex/gender intake

Personality scores show meaningful average differences by sex, particularly on Agreeableness and Emotional Sensitivity. Ignoring this would make your scores less accurate against any peer-group reference. Stille asks you to describe your sex or gender at intake (four options: Female, Male, Non-binary or other, Prefer not to say) and compares you to the matching reference group.

The underlying normative dataset only collected binary sex categories. So for non-binary respondents and those who prefer not to say, Stille uses a pooled reference (male and female samples combined) as the closest available approximation. We’re building toward a dedicated non-binary reference sample from Stille’s own data; until then, the pooled approximation is what we have, and it’s disclosed here rather than hidden.

Age intake

Personality patterns drift modestly across the lifespan — Conscientiousness and Agreeableness tend to rise; Emotional Sensitivity tends to decline. Stille stratifies its norms across six age bands (18–21, 22–29, 30–39, 40–49, 50–59, 60+) so your scores are compared to people in roughly your life-stage rather than the whole-population average.

Stille is for adults; the minimum age to take the test is 18.

Spelling

The IPIP-NEO-120 was published in US English. For the New Zealand launch, Stille administers the items with British/NZ spelling (e.g. “Sympathise with the homeless” in place of the published “Sympathize…”). The change is spelling-only — no item has had its semantic content altered. Spelling-only changes are below the threshold at which response distributions have been shown to shift in the item-translation literature, so the original norms still apply unmodified.

A note on the N5 Immoderation facet

The N5 Immoderation facet (how readily you give in to immediate desires — appetite, spending, indulgence) sits under Emotional Sensitivity (Neuroticism) in Stille, following the original NEO PI-R / IPIP-NEO-120 structure. Costa & McCrae’s reasoning was that giving in to impulses reflects an inability to regulate affect-driven urges.

Modern factor-analytic work pushes back on this placement: N5 typically loads more strongly on Conscientiousness (specifically near Self-Discipline and Cautiousness) than on Neuroticism. HEXACO (Ashton & Lee) moves impulsivity-type content out of the N analogue entirely. We’ve kept the NEO placement for v1 because Johnson’s published norms assume the original structure (moving N5 would invalidate the domain-level T-scores for both N and C). We’ll revisit when Stille has its own normative sample large enough to publish a structural deviation defensibly.

What Stille is not

Stille is for self-reflection and self-development. It is not a clinical assessment, not a diagnosis, and not a substitute for care from a registered mental health professional. Personality patterns are real but probabilistic and shift with life stages, contexts, and effort. Read your report as data about your tendencies, not a fixed truth about who you are. See the terms page for crisis-support contact details and the broader non-clinical disclaimer.

How your data is handled

The short version: stored in a Tokyo-region database, never sold, never used for advertising. The full version is on the privacy page.