Homework 6
Covers Chapters 9 and 10
Use the High School and Beyond (HSB) data set.
The data is explained in the HSB Read Me file.
USE MATH AS PREDICTOR
1.
Some researchers feel an interaction exists between Gender and Writing ability.
Create an Gender*Writing interaction term.
Based on the 14 predictor variables, how
many models are possible (assume an intercept for all models)?
2
14
= 16,384
2.
Using Math as predictor, analyze the data using Minitab Backward, Forward, and
Stepwise Regression (keep default settings).
Specify the “best” regression equation
identified by these three methods.
How many steps did it take for each method?
Do they
agree?
Backward:
Math =
32.68  2.21Gender + 1.02SES + 0.106CAR + 0.378RDG + 0.371cWRTG
Steps: 8
Forward:
Math =
32.63 + 0.362RDG + 0.362cWRTG  2.30Gender + 0.92SES + 0.103CAR
+ 0.65LOCUS + 0.34 RACE
Steps: 7
Stepwise:
Math =
33.53 + 0.367RDG + 0.365cWRTG  2.30Gender + 0.94SES + 0.99CAR
+ 0.66LOCUS
Steps: 6
Agree? No, they do not agree.
3.
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 '08
 SENTURK,DAMLA
 Regression Analysis, DI, HSB, backward elimination analysis, lowest cp

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