Statistical Sciences 1023A/B Chapter Notes - Chapter 12: Contingency Table, Dependent And Independent Variables, Categorical Variable

• School: Western University
• Department: Statistical Sciences
• Course: Statistical Sciences 1023A/B
• Professor: Lori Murray

Document Summary

Count the number of individuals who fall into each combination of categories. Categorical variable = measurements that place individuals into categories (male/female, smoker/non-smoker) Present the counts in a table = contingency table. Each row and column combination = cell. There should be enough cells to represent each combination of treatment and outcome. Variable a = explanatory variable = aspirin or placebo. Variable b = response variable = heart attack or no heart attack. Contingency table with explanatory as row variable, response as column variable, four cells. Find the row percentages: aspirin + heart attack = 104/11,037= 0. 0094 or 0. 94, placebo + heart attack = 189/11,034= 0. 0171 or 1. 71% Sometimes when the percentages are so small, they are expressed as a rate. Rate is stated as the (cid:374)u(cid:373)(cid:271)er of i(cid:374)di(cid:448)iduals per (cid:1005)(cid:1004)(cid:1004)(cid:1004) et(cid:272). depe(cid:374)di(cid:374)g o(cid:374) (cid:449)hat"s easiest to interpret. Percentage is equivalent to a rate per 100. A population contains 1000 individuals, of which 400 carry the gene for a disease.