social, personality, and community). Meehl's paradox Meehl's paradox is that in the hard sciences more sophisticated and precise methods make it harder to claim support for one's theory. The opposite is true in soft sciences like the social sciences. Hard sciences like physics make exact point predictions and work by testing whether observed data falsify those predictions. With increased precision, one is better able to detect small deviations from the model's predictions and harder to claim support for the model. In contrast, softer social sciences make only directional predictions, not point predictions. Softer social sciences claim support when the direction of the observed effect matches predictions, rejecting only the null hypothesis of zero effect. Meehl argued that no treatment in the real world has zero effect. With sufficient sample size, therefore, one should almost always be able to reject the null hypothesis of zero effect. Researchers who guessed randomly at the sign of any small effect would have a 50–50 chance of finding confirmation with sufficiently large sample size. Minnesota Multiphasic Personality Inventory Meehl was considered an authority on the development of psychological assessments using the Minnesota Multiphasic Personality Inventory (MMPI). While Meehl did not directly develop the original MMPI items (he was a high school junior when Hathaway and McKinley created the item pool), he contributed widely to the literature on interpreting patterns of responses to MMPI questions. In particular, Meehl argued that the MMPI could be used to understand personality profiles systematically associated with clinical outcomes, something he termed a statistical (versus a "clinical") approach to predicting behavior. Interactions and suppressors: the K scale As part of his doctoral dissertation, Meehl worked with Hathaway to develop the K scale indicator of valid responding for the MMPI. During initial clinical testing of the MMPI, a subset of individuals exhibiting clear signs of mental illness still produced normal personality profiles on the various clinical scales. It was suspected that these individuals were demonstrating clinical defensiveness and presenting as asymptomatic and well-adjusted. Meehl and Hathaway employed a technique called "empirical criterion keying" to compare the responses of these defensive individuals with other individuals who were not suspected of experiencing mental illness and who also produced normal MMPI profiles. The empirical criterion keying approach selected items based on their ability to maximally discriminate between these groups. They were not selected based on theory or face validity of the item content. As a