PSYC 212 Lecture Notes - Lecture 4: Interquartile Range, Box Plot, Squared Deviations From The Mean
20 Sep 2016
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Document Summary
Measures of variability: describing the spread of a distribution. What is variability: variability tells us how spread out the score in our sample are. Option 1: range: there are several different ways to describe variability. The simplest of these is the range, which is the difference between the highest score and the lowest score: problem: like the mean, the range can be influenced by outliers. Solution: the interquartile range (iqr) similar to the median, but only includes the middle 50% of scores in the distribution. If there are an even amount of numbers, split the sample in half to find the q1 and q3: subtract q1 q3 to find the iqr. Outliers: how do we know whether a score is really an outlier, outliers are scores that are either: (1. 5 x iqr) below q1 or (1. 5 x iqr) above q3. Q3 + (1. 5 x iqr: ex. Q1 = 81, q3 = 88, iqr = 7.
