Page 18 - Intermediate Statistics for Dummies

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Table of Contents
Checking the Conditions.............................................................................165
Checking off independence...............................................................166
Looking for what’s normal ................................................................166
Taking note of spread ........................................................................167
Setting Up the Hypotheses..........................................................................168
Doing the F-Test............................................................................................168
Running ANOVA in Minitab ...............................................................169
Breaking down the variance into sums of squares ........................170
Locating those mean sums of squares ............................................171
Figuring the F-statistic .......................................................................172
Making conclusions from ANOVA.....................................................173
What’s next?........................................................................................175
Checking the Fit of the ANOVA Model.......................................................175
Chapter 10: Pairing Things Down with Multiple Comparisons . . . . .177
Following Up after ANOVA ..........................................................................177
Pinpointing Differing Means with Fisher and Tukey................................180
Fishing for differences with Fisher’s LSD ........................................180 xv
Separating the turkeys with Tukey’s test........................................182
Chapter 11: Getting a Little Interaction with Two-Way ANOVA . . . .185
Setting Up the Two-Way ANOVA Model.....................................................186
Determining the treatments..............................................................186
Stepping through the sums of squares............................................186
Understanding Interaction Effects.............................................................188
What is interaction anyway?.............................................................188
Interacting with interaction plots ....................................................189
Testing the Terms in Two-Way ANOVA......................................................191
Running the Two-Way ANOVA Table..........................................................192
Interpreting the results: Numbers and graphs ...............................192
Chapter 12 Rock My World: Relating Regression to ANOVA . . . . . .195
Seeing Regression through the Eyes of Variation ....................................195
Verifying variability in the y’s and looking at x to explain it.........196
Seeing the variability in Internet use ...............................................196
Finding an “x-planation” for Internet use ........................................196
Getting results with regression.........................................................198
Assessing the fit of the regression model .......................................199
Regression and ANOVA: A Meeting of the Models...................................200
Comparing sums of squares..............................................................201
Dividing up the degrees of freedom.................................................202
Bringing regression to the ANOVA table .........................................204
Relating the F- and t-statistics: The final frontier...........................205