SOCSCI 2J03 Lecture Notes - Lecture 9: Standard Deviation, Frequency Distribution, Variance

• School: McMaster University
• Department: Social Sciences
• Course: SOCSCI 2J03
• Professor: Rizwan Tahir

Document Summary

Socsci 2j03 lecture 9 variance and standard deviation. Population data variance: denoted by (read as sigma squared) Basic formula for variance and standard deviation for ungrouped data: Find summation x , and summation x squared. Quantity x and x x in the above formulas is called deviation of x value from mean. Sum of deviations of x values from mean is always zero; that is: (x ) = 0 and (x x) = 0. Short-cut formulas for the variance and standard deviation for ungrouped data: (mann, 2016) Measure of variation: sample standard deviation equation example: Data (xi) : 10 12 14 15 17 18 18 24 n = 8 mean = x = 16. A measure of the average scatter around the mean. Find variance using standard deviation equation (for sample): (units of variance is squared in this step, not in dollars) Obtain standard deviation: take the (positive) square root of variance: