The Eysenck Personality Inventory (EPI) measures two pervasive, independent dimensions of personality, Extraversion-Introversion and Neuroticism-Stability, which account for most of the variance in the personality domain. Each form contains 57 “Yes-No” items with no repetition of items. The inclusion of a falsification scale provides for the detection of response distortion. The traits measured are Extraversion-Introversion and Neuroticism.
Instrument to measure unobserved constructs (latent variables). Typically it is a series of tasks or problems that the respondent has to solve.