Data Analysis Notes: Correlation and Regression PDF

Chapter 6: Scatterplots Association and Correlation Scatterplots: ​ A scatterplot which plots 1 quantitative variable against another, can be an effective display of data ​ Scatterplots are the ideal way to picture associations between 2 quantitative variables ​ Scatterplo...

Chapter 6: Scatterplots Association and Correlation Scatterplots: ​ A scatterplot which plots 1 quantitative variable against another, can be an effective display of data ​ Scatterplots are the ideal way to picture associations between 2 quantitative variables ​ Scatterplots: indicating if 2 variables are related. And if they are related, what is the nature of their relationship? ​ Examples where a scatterplot could be used is to determine if: gas prices vary with average monthly temperature, cholesterol varies with dietary intake, job satisfaction varies with the number of employees working in the company, sale of A/C devices varies with the average daily temperature, Sale of lawn mowers varies with the amount of rainfall Association: ​ Scatterplots are the ideal way to picture associations between 2 quantitative variables ​ Association: Is a change in the value of one variable associated with a change in the value of another variable?! ​ We may wonder if there are any associations between the following variables. And if there is one, is it positive or negative, and how strong is it? Understanding Correlation: ​ Correlation measures the strength of the linear association between two quantitative variables ​ Before you use correlation, you must check 3 conditions: 1.​ Quantitative Variables Condition: Correlation applies only to quantitative variables 2.​ Linearity Condition: Correlation measures the strength of the linear association 3.​ Outlier Condition: Unusual observations can distort the correlation Chapter 7: Introduction to Linear Regression