Latent Transition Analysis1

Appendix A

Summary of PROC LTA Statements and Options

Syntax / Required / Description
PROC LTA / √ / Invokes the procedure
options:
DATA / √ / Specifies SAS data file to be analyzed
VERBOSE_OUTPUT / Shows starting values, parameter restrictions and maximum absolute deviation and loglikelihood at each iteration
OUTEST / Saves parameter estimates to SAS data file in one record
OUTPARAM / Saves parameter estimates to SAS data file
OUTPOST / Saves posterior probabilities to SAS data file
NOPRINT / Suppresses printing of output
START / Allows user to provide starting values
RESTRICT / Allows user to specify parameter restrictions for item-response probabilities
NOBETATEST / Suppresses tests of significance for covariates
statements:
NSTATUS / √ / Specifies number of latent statuses at each time
NTIMES / √ / Specifies number of times of measurement
ITEMS / √ / Declares variables that indicate latent status variable at each time
CATEGORIES / √ / Specifies number of response categories in items
ID / Declares identifier and other variables to retain in posterior probabilities SAS file
GROUPS / Declares categorical grouping variable
GROUPNAMES / Specifies a label for each group
COVARIATES1 / Declares variables to include as covariates for Time 1 status
COVARIATES2 / Declares variables to include as covariates for transitions
REFERENCE1 / Specifies latent status to be used as reference group in prediction from COVARIATES1
REFERENCE2 / Specifies latent statuses to be used as reference groups in prediction from COVARIATES2
BINARY1 / Specifies latent status to be used as comparison group in prediction from COVARIATES1, and that binary logistic regression is to be used
BINARY2 / Specifies latent statuses to be used as comparison groups in prediction from COVARIATES2, and that binary logistic regression is to be used
STABILIZE / Invokes a stabilizing prior for the logistic regressions
FREQ / Declares frequency count variable, to use when data are aggregated
ESTIMATION / Specifies estimation procedure
SEED / √ a / Specifies seed for random number generator
MEASUREMENT / Invokes measurement invariance across groups and/or times
MAXITER / Specifies maximum number of iterations
CRITERION / Specifies convergence criterion for maximum absolute deviation

a SEED statement is required only if the START option is not included in the PROC LTA statement.

Appendix B

SAS Syntax Used to Fit LTA Models

*Model 1. Five-status Model for Dating and Sexual Behavior;

proclta data=pgm.sex_recoded;

title1 'Model 1';

nstatus 5;

ntimes 3;

items datepar_alt_98 sex_yr_98 part_98 expos_98

datepar_alt_99 sex_yr_99 part_99 expos_99

datepar_alt_00 sex_yr_00 part_00 expos_00;

categories 3232;

measurement times;

seed 592667;

run;

*Model 2. Five-status Model for Dating and Sexual Behavior, by Sex;

proclta data=pgm.sex_recoded;

title1 'Model 2';

nstatus 5;

ntimes 3;

items datepar_alt_98 sex_yr_98 part_98 expos_98

datepar_alt_99 sex_yr_99 part_99 expos_99

datepar_alt_00 sex_yr_00 part_00 expos_00;

categories 3232;

groups gender;

groupnames male female;

measurement times groups;

seed 592667;

run;

*Model 3. Time 1 Substance Use Predicting Time 1 Deltas;

procltadata=pgm.sex_recoded start=lta5_start;

title1 'Model 3';

nstatus 5;

ntimes 3;

items datepar_alt_98 sex_yr_98 part_98 expos_98

datepar_alt_99 sex_yr_99 part_99 expos_99

datepar_alt_00 sex_yr_00 part_00 expos_00;

categories 3232;

covariates1 cig_yr_98 drunk_98 mar_yr_98;

reference1 1;

measurement times;

run;

*Model 4. Time 1 Substance Use Predicting Time 1 Deltas, by Sex;

proclta data=pgm.sex_recoded start=lta5gend_start;

title1 'Model 4';

nstatus 5;

ntimes 3;

items datepar_alt_98 sex_yr_98 part_98 expos_98

datepar_alt_99 sex_yr_99 part_99 expos_99

datepar_alt_00 sex_yr_00 part_00 expos_00;

categories 3232;

covariates1 cig_yr_98 drunk_98 mar_yr_98;

reference11;

groups gender;

groupnames male female;

measurement times groups;

run;

*Model 5. Drunkenness Predicting Dating and Sexual Behavior Over Time;

proclta data=pgm.sex_recoded start=time2_start_tau rest=time2_rest_tau;

title1 'Model 5';

nstatus 5;

ntimes 2;

items datepar_alt_98 sex_yr_98 part_98 expos_98

datepar_alt_99 sex_yr_99 part_99 expos_99;

categories 3232;

covariates1 drunk_98;

covariates2 drunk_98;

reference11;

reference21 2 3 0 5;

measurement times;

run;

Appendix C

Starting Values Provided for Model 3

*Starting Values for Five-class Models;

datalta5_start;

inputparam $ group variable $ time statusrespcatestls1 estls2 estls3 estls4 estls5;

datalines;

DELTA 1 . 1 . . 0.2 0.2 0.2 0.2 0.2

TAU 1 . 1 1 . 0.2 0.2 0.2 0.2 0.2

TAU 1 . 1 2 . 0.2 0.2 0.2 0.2 0.2

TAU 1 . 1 3 . 0.2 0.2 0.2 0.2 0.2

TAU 1 . 1 4 . 0.2 0.2 0.2 0.2 0.2

TAU 1 . 1 5 . 0.2 0.2 0.2 0.2 0.2

TAU 1 . 2 1 . 0.2 0.2 0.2 0.2 0.2

TAU 1 . 2 2 . 0.2 0.2 0.2 0.2 0.2

TAU 1 . 2 3 . 0.2 0.2 0.2 0.2 0.2

TAU 1 . 2 4 . 0.2 0.2 0.2 0.2 0.2

TAU 1 . 2 5 . 0.2 0.2 0.2 0.2 0.2

RHO 1 datepar_alt_98 1 . 1 0.6 0.2 0.2 0.2 0.2

RHO 1 sex_yr_98 1 . 1 0.6 0.6 0.4 0.4 0.4

RHO 1 part_98 1 . 1 0.6 0.6 0.2 0.2 0.2

RHO 1 expos_98 1 . 1 0.6 0.6 0.4 0.6 0.4

RHO 1 datepar_alt_98 1 . 2 0.2 0.2 0.6 0.2 0.2

RHO 1 sex_yr_98 1 . 2 0.4 0.4 0.6 0.6 0.6

RHO 1 part_98 1 . 2 0.2 0.2 0.6 0.2 0.2

RHO 1 expos_98 1 . 2 0.4 0.4 0.6 0.4 0.6

RHO 1 datepar_alt_98 1 . 3 0.2 0.6 0.2 0.6 0.6

RHO 1 sex_yr_98 1 . 3 0 0 0 0 0

RHO 1 part_98 1 . 3 0.2 0.2 0.2 0.6 0.6

RHO 1 expos_99 1 . 3 0 0 0 0 0

RHO 1 datepar_alt_99 2 . 1 0.6 0.2 0.2 0.2 0.2

RHO 1 sex_yr_99 2 . 1 0.6 0.6 0.4 0.4 0.4

RHO 1 part_99 2 . 1 0.6 0.6 0.2 0.2 0.2

RHO 1 expos_99 2 . 1 0.6 0.6 0.4 0.6 0.4

RHO 1 datepar_alt_99 2 . 2 0.2 0.2 0.6 0.2 0.2

RHO 1 sex_yr_99 2 . 2 0.4 0.4 0.6 0.6 0.6

RHO 1 part_99 2 . 2 0.2 0.2 0.6 0.2 0.2

RHO 1 expos_99 2 . 2 0.4 0.4 0.6 0.4 0.6

RHO 1 datepar_alt_99 2 . 3 0.2 0.6 0.2 0.6 0.6

RHO 1 sex_yr_99 2 . 3 0 0 0 0 0

RHO 1 part_99 2 . 3 0.2 0.2 0.2 0.6 0.6

RHO 1 expos_99 2 . 3 0 0 0 0 0

RHO 1 datepar_alt_00 3 . 1 0.6 0.2 0.2 0.2 0.2

RHO 1 sex_yr_00 3 . 1 0.6 0.6 0.4 0.4 0.4

RHO 1 part_00 3 . 1 0.6 0.6 0.2 0.2 0.2

RHO 1 expos_00 3 . 1 0.6 0.6 0.4 0.6 0.4

RHO 1 datepar_alt_00 3 . 2 0.2 0.2 0.6 0.2 0.2

RHO 1 sex_yr_00 3 . 2 0.4 0.4 0.6 0.6 0.6

RHO 1 part_00 3 . 2 0.2 0.2 0.6 0.2 0.2

RHO 1 expos_00 3 . 2 0.4 0.4 0.6 0.4 0.6

RHO 1 datepar_alt_00 3 . 3 0.2 0.6 0.2 0.6 0.6

RHO 1 sex_yr_00 3 . 3 0 0 0 0 0

RHO 1 part_00 3 . 3 0.2 0.2 0.2 0.6 0.6

RHO 1 expos_00 3 . 3 0 0 0 0 0

;