Psychology 2800E Lecture Notes - Lecture 5: Discriminant Validity, Multiple Choice, Predictive Validity

• School: Western University
• Department: Psychology
• Course: Psychology 2800E
• Professor: Doug Hazlewood

Document Summary

Observed score = true score + & - random error + or systematic error (or bias) Systematic error systematically raises/lowers observed score from true score. Must minimize random and systematic error (so observed score = true score). By maximizing the reliability & validity of measures. Part 1: reliability (minimizing random error: the more is better rule. Random error will cancel itself out over repeated measurements. Example 1: beating vince carter in basketball. Example 2: grandfathers who can"t believe it : we can decrease random error by increasing the reliability of our measures. A measure is reliable if it measures things consistently: types of reliability. Relevant when measure consists of multiple item (e. g. exam) Inconsistency can be a sign of random error. Item-total correlations (if random error is low, responses to any single item should be positively correlated with total score) Eliminate items with low item-total correlations (and/or add more items)