2/20/2026

Identifying unusual points in regression - Section 4.4

• Identifying unusual residuals and influential points
  • Standardized residuals
  • Studentized residuals
  • Leverage
  • Cook's distance
  • dffits
  • dfbetas

Coding Categorical Variables - Section 4.5 - covered in PS with manduca sexta exercises

Randomization test for a relationship - Section 4.6 - covered on permutation test handout

Bootstrap for Regression - Section 4.7 - extremely valuable

• See GoogleDrive\Stat206-DataAnalysis-F2025\2ePowerPoint\Sec4.7R

R Demonstration

• See GoogleDrive\Stat206-DataAnalysis-F2025\2eMarkkdown\Sec4.4.Rmd
• See GoogleDrive\Stat206-DataAnalysis-F2025\2eMarkkdown\Sec4.7.Rmd

R LAB

• Bootstrapping handout - alternative inference methods
• Identify unusual and influential points in the perch data and the StateSAT data.
• Use best subsets and stepwise regression to identify the best model for predicting winning percentage for MLB teams in MLB2007Standings. (See Exercise 4.3 on p. 188.)

We will have a problem session on Monday.