SAS Program Analysis: Regression Models with and without Interaction Terms - Prof. Mervyn , Study notes of Statistics

This document showcases a sas program that performs regression analysis on a dataset with two variables, time and humidity, to predict wtloss. The program creates two regression models, one with interaction terms and the other without. The analysis includes descriptive statistics, anova, and parameter estimates.

Typology: Study notes

Pre 2010

Uploaded on 09/02/2009

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EXAMPLE D13
SAS Program
data evap;
input wtloss time humid;
time=time-5.5;
humid=humid-.3;
humidsq=humid*humid;
timehumid=time*humid;
timehumidsq=time*humidsq;
datalines;
4.3 4 .2
5.6 5 .2
6.4 6 .2
8.0 7 .2
4.0 4 .3
5.2 5 .3
6.6 6 .3
7.5 7 .3
3.2 4 .4
4.0 5 .4
5.6 6 .4
6.4 7 .4
;
run;
proc reg;
model wtloss= time humid humidsq timehumid timehumidsq/vif;
model wtloss= time humid humidsq;
title 'Regressiom Models with and without Interaction Terms';
run;
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EXAMPLE D13SAS Program data

evap; input

wtloss time humid; time=time-

humid=humid-

humidsq=humidhumid;timehumid=timehumid;timehumidsq=time*humidsq;datalines;4.3 4 .25.6 5 .26.4 6 .28.0 7 .24.0 4 .35.2 5 .36.6 6 .37.5 7 .33.2 4 .44.0 5 .45.6 6 .46.4 7 .4; run

proc

reg

model

wtloss= time humid humidsq timehumid timehumidsq/vif; model

wtloss= time humid humidsq; title

'Regressiom Models with and without Interaction Terms'; run

SAS Log 3

data

evap;

4

input

wtloss

time

humid;

time=time-5.5; 6

humid=humid-.3; 7

humidsq=humid*humid; 8

timehumid=time*humid; 9

timehumidsq=time*humidsq; 10

datalines; NOTE:

The

data

set

WORK.EVAP has 12 observations

and 6 variables.

NOTE:

DATA

statement

used (Total

process time):

real

time

0.09 seconds

cpu

time

0.01 seconds

run; 2526

proc

reg;

27

model

wtloss=

time

humid

humidsq

timehumid

timehumidsq/vif;

model

wtloss=

time

humid

humidsq;

title

'Regressiom

Models with and

without Interaction Terms';

run;

Parameter

Estimates

Parameter

Standard

Variance

Variable

DF^

Estimate

Error

t^ Value

Pr^

^ |t|

Inflation

Intercept

time

humid

humidsq

timehumid

timehumidsq

Regressiom

Models

with

and

without

Interaction

Terms

The

REG

Procedure Model:

MODEL

Dependent

Variable:

wtloss

Number

of

Observations

Read

Number

of

Observations

Used

Analysis

of VarianceSum^

of^

Mean

Source

DF^

Squares

Square

F^ Value

Pr^

>^ F

Model

Error

Corrected

Total

Root

MSE

R-Square

Dependent

Mean

Adj

R-Sq

Coeff

Var