PSYC 3000 Lecture Notes - Lecture 3: Interquartile Range, Quartile, Box Plot

• School: Carleton University
• Department: Psychology
• Course: PSYC 3000
• Professor: Bruce Hutcheon

Document Summary

For normal distribution, we try and find the center of the data using the sample mean. Dispersion means how observation are dispersed around the centre. Often in research we don"t get normal distribution. Mean doesn"t work well in skewed or oddly shaped distribution. Another solution is to use quartiles across the distribution. Separating the distribution by quartiles allows us to establish landmarks and notice any outliers. Interquartile range is the difference between one quartile to another (q3-q1) A display of different landmarks on a distribution (quartiles) It is not always in the middle of the box, it just needs to be inside the box. Most of the time it is shown vertically. The size of the box is the interquartile range (q3-q1) Width of the box does not matter, simply visual effect. In the boxplot there is an invisible line. Whisker (line on top of and bottom of box) always ends on a data point.