Mini-IPIP

The Mini-IPIP is a concise assessment of the five factor model of personality. It contains only 20 questions and can usually be completed in less than five minutes, yet maintains good psychometric properties (see below). The test was created using items from the open source project called the International Personality Item Pool (IPIP).

Validity

In test theory, validation refers to the level of evidence that supports the ability of users to draw useful, accurate, and truthful inferences/interpretations from a measure. In other words, validity refers to an instrument measuring what it says it measures and the ability of results to generalize to real-world outcomes. Three types of validation include:

Content validity

Ability to infer from test measures to larger construct domains; the degree to which the instrument measures all facets of what it says it measures

According to Donnellan et al. (2006), the Mini-IPIP is derived from the larger 50 item IPIP-FFM (see Goldberg, 1999) and was reduced to the top four items for each trait scale, using exploratory factor analysis as the primary method for selecting items that loaded most highly on a single trait [while maintaining balance between positive and negative keyed items]. The same study confirms that factor component loadings of the IPIP-NEO-120 are representitive of the five major personality traits.

Criterian validity

Ability to make inferences from test scores to another real-world behaviors

Mini-IPIP

Five Factors (OCEAN Traits)

Individual, Interpersonal, and Social Life Outcomes

As summarized in Soto (2019), effect sizes between the five factors and important life outcomes are generally between r = .20 - .40 (p < .05 - .01).

Construct validity

Ability to make inferences from test scores to various psychological constructs (e.g., characteristics grouped as personality traits) ; the overall confidence that a test measures what it claims to measure

The five factor theory was popularized by Norman (1963) as an "adequate taxonomy of personality attributes" - it factor analyzed scores from various personality trait scales into five distinct factors. Later, a test called the NEO was created from this earlier body of work and used the familiar OCEAN trait categories: McCrae & Costa (1985) provided validation data for their NEO assessment.

Donnellan et al. (2006) document scale correlations between the Mini-IPIP and its longer-form parent assessment (average r = 0.9; see test characteristics table below). Confirmatory Factor Analysis indicated an acceptable fit: Root Mean Square Error of Approximation (RMSEA) = 0.07 (p < .05).

Reliability

Reliability refers to the consistency and repeatability of test scores or measurements. It answers the question, how likely is an individual to obtain the same score if the same measure is repeatedly administered to them?

Inter-rater reliability

Assesses the degree of agreement between two or more raters in their appraisals.

Many studies have explored the extent that different observers ratings are different than self-ratings when evaluating the five factors. In particular, Kim et al. (2019) conducted a meta analysis of over 150 studies examining the degree that big five ratings from friends, family, colleagues, and strangers would differ from self-ratings. Overall, no significant differences were found (average effect δ = −.038) indicating good consistency between self and other ratings across various methods of assessment.

Test-retest reliability

Assesses the degree to which test scores are consistent from one test administration to the next.

McCrae et al. (2010) indicates that the big five personality traits generally have strong retest stability when readministered to the same participants after 1 week (retest rs = .91-.93) and over the course of 6 years (retest rs = .87-.93). Trait consistency for Neuroticism, Extraversion, Openness, and Agreeableness peaks in middle age whereas Conscientiousness continuously stabilizes over time. Trait scores are also influenced by life events (Specht et al., 2011).

For the Mini-IPIP, Donnellan et al. (2006) found 3-week retest correlations of between rs = .62 (Agreeableness) to .87 (Extraversion).

Inter-method reliability

Assesses the degree to which test scores are consistent when there is a variation in the methods or instruments used.

As demonstrated in Donnellan et al. (2006), convergent / scale correlations between Mini-IPIP and the following methods of measuring the five factors are relatively high:

IPIP FFM rs = .85 to .93
Informant ratings rs = .26 to .53

Internal consistency reliability

Assesses the consistency of results across items within a test.

The alpha coefficient is a measure of reliability. It increases with fewer measurement errors of an assessment's items and when items are measuring a single construct.

Donnellan et al. (2006) reports alpha coefficients from a large college sample (n = 2,663) of users who completed the Mini-IPIP:

Neuroticism: α = .68
Extraversion: α = .77
Openness to experience: α = .65
Agreeableness: α = .70
Conscientiousness: α = .69

Supporting Test Characteristics

Big-Five Domain	Number of Items	Coefficient Alpha (+ / -)	Correlation with Parent Scale
I. Extraversion	2 + 2 = 4	0.77	.93 [.78]
II. Agreeableness	2 + 2 = 4	0.7	.89 [.67]
III. Conscientiousness	2 + 2 = 4	0.69	.90 [.67]
IV. Neuroticism	2 + 2 = 4	0.68	-.92 [.76]
V. Intellect	1 + 3 = 4	0.65	0.85 [.56]
Total/Mean	9 + 11 = 20	0.7	.90

Adapted from the IPIP website

Notes

The numbers under the "(+ / -)" heading indicate the number of positively and negatively items in the scale.
Values in brackets represent correlations between non-duplicate items from the parent test scales.

References

Donnellan, M. B., Oswald, F. L., Baird, B. M., & Lucas, R. E. (2006). The Mini-IPIP scales: Tiny-yet-effective measures of the Big Five factors of personality. Psychological Assessment, 18, 192-203. http://doi.org/10.1037/1040-3590.18.2.192

Goldberg, L. R. (1999). A broad-bandwidth, public domain, personality inventory measuring the lower-level facets of several five-factor models. In I. Mervielde, I. Deary, F. De Fruyt, & F. Ostendorf (Eds.), Personality Psychology in Europe, Vol. 7 (pp. 7-28). Tilburg, The Netherlands: Tilburg University Press. https://ipip.ori.org/A%20broad-bandwidth%20inventory.pdf

Kim, H., Di Domenico, S. I., & Connelly, B. S. (2019). Self–other agreement in personality reports: A meta-analytic comparison of self- and informant-report means. Psychological Science, 30(1), 129-138. http://doi.org/10.1177/0956797618810000

McCrae, R. R., & Costa, P. T. (1985). Updating Norman's 'adequacy taxonomy': Intelligence and personality dimensions in natural language and in questionnaires. Journal of Personality and Social Psychology, 49(3), 710-721. http://doi.org/10.1037/0022-3514.49.3.710

McCrae, R. R., Kurtz, J. E., Yamagata, S., & Terracciano, A. (2011). Internal consistency, retest reliability, and their implications for personality scale validity. Personality and Social Psychology Review, 15(1), 28-50. http://doi.org/10.1177/1088868310366253

Norman, W. T. (1963). Toward an adequate taxonomy of personality attributes: Replicated factor structure in peer nomination personality ratings. The Journal of Abnormal and Social Psychology, 66(6), 574-583. http://doi.org/10.1037/h0040291

Soto, C. J. (2019). How Replicable Are Links Between Personality Traits and Consequential Life Outcomes? The Life Outcomes of personality Replication Project. Psychological Science, 30(5), 711-727. https://doi.org/10.1177%2F0956797619831612

Specht, Jule & Egloff, Boris & Schmukle, Stefan. (2011). Stability and Change of Personality Across the Life Course: The Impact of Age and Major Life Events on Mean-Level and Rank-Order Stability of the Big Five. Journal of Personality and Social Psychology. 101. 862-882. https://doi.org/10.1037/a0024950