P R 309 Study Guide - Midterm Guide: Standard Deviation, Statistical Significance
Document Summary
Defined as the number of standard deviations from the mean. Useful in comparing variables with very different observed units of measurement. Allows for precise predictions to be made of how many of a population"s scores fall within a score range in a normal distribution. The sign of any z-score indicates the direction of a score: whether that observation fell above the mean (the positive direction) or below the mean (the negative direction) If a raw score is below the mean, the z-score will be negative, and. Standard deviation: a measure of dispersion that defines how an individual entry differs from the mean. Defines the shape of the normal distribution curve. 50% of the scores fall above the mean and 50% fall below. Approximately 68% of the scores fall within plus and minus. 99. 7% of the scores fall within plus and minus 3 z-scores from the mean. Z-scores allow us to compare variables with very different observed units of measure.
