Chapter 04 Notes - Scatterplots and Correlation - STAT 1450 COURSE NOTES CHAPTER 4 SCATTERPLOTS AND CORRELATION Guided Notes associated with the Lecture

Chapter 04 Notes - Scatterplots and Correlation - STAT 1450...

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S TAT 1450 C OURSE N OTES – C HAPTER 4 S CATTERPLOTS AND C ORRELATION Guided Notes associated with the Lecture Videos for Sections 4.1 & 4.2 Connecting Chapter 4 to our Current Knowledge of Statistics Our conversation to date has focused on counts or measurements of one variable. We will extend the conversation to measure a pair of quantitative variables. 1. List 3 quantitative variables that might influence how much someone’s monthly rent amount. 2. Classify each of the 4 variables (including monthly rent) as either a cause or an effect . 4.1 Explanatory and Response Variables A response (dependent) variable measures an outcome of a study. EFFECT An explanatory (independent) variable explains or influences changes in a response variable. CAUSE Typically, the explanatory variable is plotted on the x -axis, and the response variable is plotted on the y -axis. If there is no explanatory-response distinction, either variable can go on the x -axis. Sometimes we would like to show a causal relationship between the two variables (where one or more explanatory variable(s) causes a change in the response variable). More will be discussed about this later on in Chapter 8. Chapter 4, page 1
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4.2 Displaying Relationships: Scatterplots A scatterplot shows the relationship between two quantitative variables measured on the same individuals. In this graph, each individual appears as a point corresponding to the value of both variables for that individual. Technology Tips – Creating Scatterplots TI-83/84 Enter the data into L 1 (explanatory, x) and L 2 (response, y). 2 nd     Y= (Stat Plot)    Enter                          Adjust your window                            ( On; highlight scatterplot; identify XList, YList1, and the ‘mark’ .)                       Zoom    9 (ZoomStat). JMP Enter the data. Analyze    Fit Y by X. Click-and-Drag ” (the response variable)                          into the  ‘Y, Response’  box.  Click-and-Drag ” (the explanatory variable)                          into the  ‘X, Factor’  box.   Click  on  OK. Example: An economist investigated the relationship between the Proportion of Residents with at least 4 Years of College & the Percentage Growth in Per Capita Income. Proportion of Residents with at least 4 Years of College 9.9 11.4 8.1 14.7 8.5 12.5 Percentage Growth in Per Capita Income 37.1 43 33.4 47.1 26.5 40.2 Does there appear to be a relationship between the Proportion of Residents with at least 4 Years of College & the
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