PY 211 Lecture Notes - Lecture 7: Interquartile Range, Standard Deviation, Variance

• School: University of Alabama
• Department: Psychology
• Course: PY 211
• Professor: Beverly B Roskos- Ewoldsen

Document Summary

Variability is the dispersion (spread) of data in a distribution. The difference between the largest value (l) and smallest value (s) in a set of data. Range = largest smallest: only considers the largest and smallest values in distribution, simplest way to describe the dispersion of scores, informative for data without outliers . Range = 21 5 = 16 (more dispersed: range, interquartile range, variance. The variance: definition, population variance definitional formula. X = 2 + 3+4+5+6 = 20: scores: 5, 14, 7, 21, 13, 8, scores: 5, 6, 7, 7, 4, 8. Range = 8 4 = 4: scores: 5, 7, 8, 20, 19, 21. Range = 21 5 = 16: deviation, average deviation, how far a score is from the mean, deviation = x - (population, deviation = x m (sample) average deviation = (x- ) / n. = x / n = 20 / 5 = 4 x.