Example:
Shuttle Missions
•
•
•
•
•
O-rings failed in Challenger disaster
Low temperature
Prior flights “erosion” and “blowby” in O-rings
Feature: Temperature at liftoff
Target: problem (1) - erosion or blowby vs. no
problem (0)
Data Shuttle;
input Atrisk failed temp LCpress launch;
label temp= "Temperature at Liftoff";
label launch = "Launch number";
label LCpress = "Leak Check pressure (PSI)";
cards;
6 0 66 50 1
6 1 70 50 2
(more data)
*;
proc logistic data=shuttle; title3 "Logistic Regression";
model failed/atrisk = temp launch;
output out=out1 predicted = p; run;
proc genmod data=shuttle; title3 "Logistic Regression";
model failed/atrisk = temp launch/dist=binomial;
run;
Chi-Square Contingency Tables
Heart Disease
No
Yes
Low
BP
High
BP
Heart Disease
No
Yes
95
5
100
75
25
55
45
100
75
25
DEPENDENT
INDEPENDENT
c2 Test Statistic
• Expect 100(150/200)=75 in upper left if independent
(etc. e.g. 100(50/200)=25)
Heart Disease
No
Yes
Low
BP
High
BP
95
(75)
55
(75)
5
(25)
45
(25)
(observed  exp ected ) 2
c  allcells
exp ected
2
100
100
2(400/75)+
2(400/25) =
42.67
Compare to
150
50
200
c2 Tables
Distribution: Chi-square df=(rows-1)(cols-1) Significant!
Next: Contingency table notes and Titanic survival example