PSYC 241 Lecture 5: Lecture 5: Z-scores
Document Summary
Central tendency: one number that describes typical score (mean, median, mode) Variability: quantitative measure of the degree to which scores in a distribution are spread out or clustered together. Normal distributions are precisely defined and always the same shape. If you randomly choose a score from a normal distribution, it is most likely to be the mean. If you rephrase the question in terms of "how close would the score be to the mean," it is most likely to be within one standard deviation of the mean. Our goal is to identify exactly where any score lies in this distribution. Raw score (x value) provides little information about comparison to other scores in distribution. Score may be relatively low, average, or high. If raw score is transformed into z-score, the z-score tells us exactly where the score is located relative to all the other scores. Changing and x value into a z-score creates a signed number.
