Cronbach's Alpha
A statistic measuring internal consistency — how closely related a set of test items are as a group. Values above 0.70 indicate acceptable reliability for personality scales.
Cronbach's alpha (α) is the most commonly reported reliability metric in psychology. It measures whether the questions in a test are all measuring the same underlying construct.
For example, if a Big Five Extraversion scale has α=0.85, it means the 10 extraversion questions are highly correlated with each other — they're all measuring the same thing. Values: below 0.60 = poor, 0.60-0.70 = questionable, 0.70-0.80 = acceptable, 0.80-0.90 = good, above 0.90 = excellent.
JobCannon tests target α=0.70-0.90 per dimension. Short social media quizzes typically have α below 0.50, making their results essentially random.