STAT 101 Lecture Notes - Lecture 2: Standard Deviation, Quartile, Interquartile Range

• School: Simon Fraser University
• Department: Statistics
• Course: STAT 101
• Professor: Harasha Perera

Document Summary

Measuring center: the mean: the most common measure of center is the arithmetic average, or mean, to find the mean, (cid:894)pro(cid:374)ou(cid:374)(cid:272)ed (cid:862)x-(cid:271)ar(cid:863)(cid:895), of a set of o(cid:271)servatio(cid:374)s, add their values and divide by the number of observations. If the n observations are x1, x2, x3, , xn, their mean is: x. Because the mean cannot resist the influence of extreme observations, it is not a resistant measure of center. Another common measure of center is the median. The median, m, is the midpoint of a distribution, the number such that half of the observations are smaller and the other half are larger. To find the median of a distribution: x i n: arrange all observations from smallest to largest, if the number of observations n is odd, the median m is the center observation in the ordered list. 1)/2 observations from the start of the list.