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From |
"Stein Atle Lie" <Stein.Lie@smis.uib.no> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: gllamm: Two-phase study with non-random missing? |

Date |
Fri, 11 Nov 2005 13:53:04 +0100 |

Dear list members Any bright ideas on this? In a troublesome population study over two phases we have non-random missing information. In the first phase there are two sources/informants screening the population (y1_1 and y1_2: 0=negative, 1=positive, and -1=missing). For the second phase diagnosis is evaluated for a sub-sample using a more precise tool (y2: 0=No, 1=Diagnosis, -1=missing). (This is not a random sample, due to several factors.) wt1 is the number of cases with the patterns of y1_1, y1_2 and y2. y1_1 y1_2 y2 wt1 patt -1 0 -1 1929 1 -1 1 -1 615 2 0 -1 -1 303 3 0 -1 0 4 4 0 0 -1 4769 5 0 0 0 352 6 0 0 1 6 7 0 1 -1 370 8 0 1 0 180 9 0 1 1 17 10 1 -1 -1 78 11 1 -1 0 9 12 1 -1 1 2 13 1 0 -1 266 14 1 0 0 203 15 1 0 1 25 16 1 1 -1 214 17 1 1 0 122 18 1 1 1 87 19 This should (?) be able to set up in gllamm, or...? I generate the long-data-file with all responses (for y1_1, y1_2 and y2) different from -1 in one variable (e.g. y) Thus patt=1 will have one line and e.g. patt=6 will have 3 lines. Furthermore, I make 3 dummy variables for where the information in response is obtained (y1_1, y1_2, or y2), and if the information in the given pattern is valid for each of the variables (non-missing: Vy1_1, Vy1_2 and Vy2) or not (missing: nVy1_1, nVy1_2 and nVy2). The problem is not very different from example 14.3, page 422, in Generalized Latent Variable Modeling by Skrondal and Rabe-Hesketh. See also: http://www.gllamm.org/books/readme.html (However, they only have missing information for one measurement) My rather extensive problem is thus: Problem1: To set up the Exposure model, Measurement model, and Disease model. It becomes a long (!) row of equations (there must be potential to reduce the problem?!) Problem2: To find good documentation for the constraints-syntax. Problem3: The total syntax for this problem in gllamm. Problem4: Last the idea is to run gllapred to estimate population probabilities e.g for P(y2=1). Regards S.A. Lie Stein.Lie@halos.uib.no * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

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