Download Homework 5

Homework #5 – PH6415
Do the analyses for these problems using SAS (except problem 1 – do this by hand).
Copy your program and SAS output into Microsoft Word and answer any remaining
questions by hand.
Also remember, a SAS data set consists of rows and columns. Each row represents an
individual unit (such as a person, plant, country, etc.) on which data was collected. Each
column represents a variable.
See examples from SAS tutorials.
Example
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HOMEWORK ASSIGNMENT: PAGANO’S BOOK
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Problem 1:
Chapter 21, page 511, number 7

This problem does
questions by hand
draw the curve by
not involve SAS programming. Answer
(type into MS Word). You can either
hand, use SAS or use Excel.
Problem 2:
Chapter 21, page 512, number 8


These data are attached to the assignment cyto.txt.
You will need to enter the data into your SAS program
using the infile statement.
The text has a misprint – drug = 2 is placebo.
*** PROBLEM 2 *****;
DATA cyto;
INFILE 'C:\cyto.txt' firstobs=2;
Input time death drug;
*the book has a misprint, for placebo drug=2, we switch this to zero
below;
data cyto;set cyto;
if drug ne 1 then drug=0;
*print data to output screen to make sure it worked;
proc print;
run;
Problem 3:
Chapter 21, page 512, number 9


These data are attached to the assignment in
bladder.txt. You will need to enter the data into
your SAS program using the infile statement.
Data coded as follows (try to recode on your own, use
problem 2 above as reference):
o Placebo: group=1
o Drug: group=2
o Time until first tumor in months: time
o Recurrence: censor=1
o No Recurrence or censored: censor=0
Problem 4:
[Adapted From: Survival Analysis Using SAS: A Practical Guide by Paul D. Allison]
1. The SAS dataset called breast.txt contains survival data for 45 patients diagnosed with
breast cancer and entered into a study. The following variables are on the dataset:
Variable
Description
Surv
Follow-up time in months after enrollment in study (surgery)
Status
Indicator variable (Status =1 if patient died, Status = 0 if patient
censored)
Met a
Meta=1 if tumor had a positive marker for metastasis, otherwise
Meta=0;
Trt
Trt=1 if new therapy, Trt=0 if standard of care
You can read the data set into SAS with the following code:
data breast;
infile 'C:\breast.txt' dsd dlm=' ' firstobs=2;
input surv status meta trt;
run;
( a)
The spread of a cancer to a new part of the body is called metastasis. Generate a
survival plot for meta=1 and meta=0 on the same graph. Is there statistical evidence
of different survival rates for patients who have a positive marker for metastasis?
What is the estimated median survival in months for each of the two types?
(b)
Generate a survival plot for trt=1 and trt=0 on the same graph. Is there statistical
evidence of different survival rates for patients who have the new treatment? What is
the estimated median survival in months for each of the two types?
( c)
What percent of people were still alive after 181 months in the standard therapy
group? What percent of people were still alive after 181 months in the new therapy
group?
(d)
Generate a survival plot for trt=1 and trt=0 for those with the positive marker for
metastasis on the same graph. For those with meta=1, is there statistical evidence of
different survival rates for patients who have the new treatment?