data cpu;
infile "C:\Lecture notes\week6\cpudat.txt";
input time line step device;
linet=line/1000;
label time="CPU time in seconds" line="lines in program execution" 
step="number of computer programs" device="mounted devices" linet="lines in program (thousand)";

proc corr data=cpu;
run;
proc gplot data=cpu;
plot time*(linet step device);
/* Regression analysis*/
proc reg data=cpu;
model time=linet step device;*/noint;
plot student.*predicted./nostat; 
plot student.*(linet step device)/nostat;
plot npp.*student./nostat ;
run; quit;

/* Steps to compute the predicted value of Y & 
the prediction interval or the 95% C.I. for the average response).
See lecture 6 notes.*/  
data predict;
input time line linet step device;
datalines;
. . 7 6 3
;
data pred;
set predict cpu;
proc print data=pred;
run;
/* Refit the regression model. 
The option clm computes the 95% C.I. 
for the predicted average response
The option cli computes the prediction interval 
for the predicted response*/
proc reg data=pred;
model time=linet step device/clm cli;
run;quit;