Sociology 2205A/B Lecture Notes - Lecture 4: Skewness, Squared Deviations From The Mean, Standard Deviation

• School: Western University
• Department: Sociology
• Course: Sociology 2205A/B
• Professor: Zajacova

Document Summary

Least squares: the sum of squared deviations is smallest possible for the mean. The middle number in an ordered list of values. If even n, average of the middle 2 values. Interpretation: the 50% percentile, 1/2 of sample have larger values, 1/2 smaller. Usage in practice: for skewed variables or if outliers. Suppose we measure the number of times per week students go to the grocery store in a sample of 5 students. Order the values from smallest to largest- 0,1,1,2,3. If even n? find the mean of middle 2 values. When a distribution has a few very high or low scores (outliers), the mean will be pulled in the direction of the extreme scores. For a positive skew, the mean is greater than the median. For a negative skew, the mean is less than the median. The greater the dispersion of a variable, the greater the range of scores and differences among scores.