STT 212 Lecture Notes - Lecture 14: Chi-Squared Test, Chi-Squared Distribution, Null Hypothesis

• School: University of Rochester
• Department: Statistics
• Course: STT 212
• Professor: Mcdermott

Document Summary

There are basically two types of random variables and they yield two types of data: numerical and categorical. A chi square ( x 2 ) statistic is used to investigate whether distributions of categorical variables differ from one another. Basically categorical variable yield data in the categories and numerical variables yield data in numerical form. Responses to such questions as "what is your major?" or do you own a car?" are categorical because they yield data such as "biology" or "no. " In contrast, responses to such questions as "how tall are you?" or "what is your g. p. a. ?" are numerical. Numerical data can be either discrete or continuous. The table below may help you see the differences between these two variables. Chi square = 105[(36)(25) - (14)(30)] 2 / (50)(55)(39)(66) = 3. 418. Before we can proceed we eed to know how many degrees of freedom we have.