Page 11 - Statistics II for Dummies

Table of Contents
No Conclusion Left Behind: Tests and Confi dence Intervals ix
for Regression ............................................................................................63
Scrutinizing the slope ..........................................................................64
Inspecting the y-intercept ...................................................................66
Building confidence intervals for the average response ................68

Making the band with prediction intervals ......................................69
Checking the Model’s Fit (The Data, Not the Clothes!) ............................71
Defining the conditions .......................................................................71

Finding and exploring the residuals ..................................................73
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Using r to measure model fi t .............................................................76
Scoping for outliers .............................................................................77
Knowing the Limitations of Your Regression Analysis .............................79
Avoiding slipping into cause-and-effect mode .................................79
Extrapolation: The ultimate no-no .....................................................80
Sometimes you need more than one variable ..................................81
Chapter 5: Multiple Regression with Two X Variables. . . . . . . . . . . . .83
Getting to Know the Multiple Regression Model .......................................83
Discovering the uses of multiple regression ....................................84
Looking at the general form of the multiple regression model......84
Stepping through the analysis ...........................................................85
Looking at x’s and y’s ....................................................................................85
Collecting the Data ........................................................................................86
Pinpointing Possible Relationships .............................................................88
Making scatterplots .............................................................................88
Correlations: Examining the bond .....................................................89
Checking for Multicolinearity ......................................................................91
Finding the Best-Fitting Model for Two x Variables ..................................92
Getting the multiple regression coeffi cients ....................................93
Interpreting the coeffi cients ...............................................................94
Testing the coeffi cients .......................................................................95
Predicting y by Using the x Variables .........................................................97
Checking the Fit of the Multiple Regression Model ..................................98
Noting the conditions ..........................................................................98
Plotting a plan to check the conditions ............................................98
Checking the three conditions .........................................................100
Chapter 6: How Can I Miss You If You Won’t Leave?
Regression Model Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .103
Getting a Kick out of Estimating Punt Distance .......................................104
Brainstorming variables and collecting data .................................104
Examining scatterplots and correlations ........................................106

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