Stat Computing > SUDAAN > FAQ

SUDAAN FAQ 
How do I analyze survey data with a two-stage cluster with unequal probabilities design?

This example is taken from Levy and Lemeshow's Sampling of Populations.

page 350 cluster sampling with unequal probabilities:  probability proportional to size sampling
This example uses the hospslct data set.

proc descript data = hospslct filetype=sas design = wr means totals;
  nest drawing/psulev = 1;
  weight wstar;
  var lifethrt dxdead;
run;

Number of observations read    :     50    Weighted count :    50056
Denominator degrees of freedom :      4

Variance Estimation Method: Taylor Series (WR)
by: Variable, One.

-----------------------------------------------------
|                 |                  |
| Variable        |                  | One
|                 |                  | 1            |
-----------------------------------------------------
|                 |                  |              |
| LIFETHRT        | Sample Size      |           50 |
|                 | Weighted Size    |     50056.00 |
|                 | Total            |      6006.72 |
|                 | SE Total         |      1001.12 |
|                 | Mean             |         0.12 |
|                 | SE Mean          |         0.02 |
-----------------------------------------------------
|                 |                  |              |
| DXDEAD          | Sample Size      |           50 |
|                 | Weighted Size    |     50056.00 |
|                 | Total            |      2002.24 |
|                 | SE Total         |      1226.12 |
|                 | Mean             |         0.04 |
|                 | SE Mean          |         0.02 |
-----------------------------------------------------

proc ratio data = hospslct filetype = sas design = wr;
  nest drawing / psulev =1;
  weight wstar;
  numer dxdead;
  denom lifethrt;
run;

Number of observations read    :     50    Weighted count :    50056
Denominator degrees of freedom :      4

Variance Estimation Method: Taylor Series (WR)
by: Variable, One.

---------------------------------------------------
|                 |                  |
| Variable        |                  | One
|                 |                  | 1          |
---------------------------------------------------
|                 |                  |            |
| DXDEAD/LIFETHRT | Sample Size      |         50 |
|                 | Weighted Size    |   50056.00 |
|                 | Weighted X-Sum   |    6006.72 |
|                 | Weighted Y-Sum   |    2002.24 |
|                 | Ratio Est.       |       0.33 |
|                 | SE Ratio         |       0.23 |
---------------------------------------------------

Page 353 cluster sampling with unequal probabilities:   probability proportional to size sampling

data hspslct2;
  set hospslct;
  /*n is 50*/
  /*N_i is admiss*/
  /* X is 7087, the total number of life-threating conditions across all the hospitals*/
  /*X_i is tl, the total number of life-threating conditions for each hospital*/
  if hospno = 2 then  tl = 785; 
  if hospno = 5 then  tl = 3404; 
  if hospno = 9 then  tl = 778; 
  w2star = (admiss/50)*(7087/tl);
run;

proc descript data = hspslct2 filetype = sas means totals;
  nest drawing/psulev=1;
  weight w2star;
  var lifethrt dxdead;
run;

Number of observations read    :     50    Weighted count :    51345
Denominator degrees of freedom :      4

Variance Estimation Method: Taylor Series (WR)
by: Variable, One.

-----------------------------------------------------
|                 |                  |
| Variable        |                  | One
|                 |                  | 1            |
-----------------------------------------------------
|                 |                  |              |
| LIFETHRT        | Sample Size      |           50 |
|                 | Weighted Size    |     51345.00 |
|                 | Total            |      6259.18 |
|                 | SE Total         |      1277.32 |
|                 | Mean             |         0.12 |
|                 | SE Mean          |         0.02 |
-----------------------------------------------------
|                 |                  |              |
| DXDEAD          | Sample Size      |           50 |
|                 | Weighted Size    |     51345.00 |
|                 | Total            |      1760.47 |
|                 | SE Total         |      1079.04 |
|                 | Mean             |         0.03 |
|                 | SE Mean          |         0.02 |
-----------------------------------------------------

proc ratio data = hspslct2 filetype = sas;
  nest drawing/psulev=1;
  weight w2star;
  numer dxdead;
  denom lifethrt;
run;

Number of observations read    :     50    Weighted count :    51345
Denominator degrees of freedom :      4

Variance Estimation Method: Taylor Series (WR)
by: Variable, One.

---------------------------------------------------
|                 |                  |
| Variable        |                  | One
|                 |                  | 1          |
---------------------------------------------------
|                 |                  |            |
| DXDEAD/LIFETHRT | Sample Size      |         50 |
|                 | Weighted Size    |   51345.00 |
|                 | Weighted X-Sum   |    6259.18 |
|                 | Weighted Y-Sum   |    1760.47 |
|                 | Ratio Est.       |       0.28 |
|                 | SE Ratio         |       0.21 |
---------------------------------------------------

UCLA Researchers are invited to our Statistical Consulting Services
We recommend others to our list of Other Resources for Statistical Computing Help
These pages are Copyrighted (c) by UCLA Academic Technology Services