Table 4.
Empirical frequencies of selecting each working correlation structure out of 1,000 replications from the use of the given correlation selection criterion. The Mancl and DeRouen [8] correction is utilized.
| Selection Frequencies | ||||||
|---|---|---|---|---|---|---|
| True | Ind | Exch | AR-1 | Toeplitz | ||
| Correlation | N | Criterion | ||||
| Exchangeable | 25 | TECMT | 16 | 387 | 109 | 488 |
| TECMR | 31 | 669 | 141 | 159 | ||
| CICT | 15 | 299 | 90 | 596 | ||
| CICR | 24 | 705 | 126 | 145 | ||
| Exchangeable | 50 | TECMT | 0 | 405 | 57 | 538 |
| TECMR | 1 | 706 | 90 | 203 | ||
| CICT | 0 | 285 | 48 | 667 | ||
| CICR | 1 | 730 | 74 | 195 | ||
| AR-1 | 25 | TECMT | 17 | 115 | 328 | 540 |
| TECMR | 33 | 184 | 599 | 184 | ||
| CICT | 14 | 74 | 287 | 625 | ||
| CICR | 34 | 168 | 628 | 170 | ||
| AR-1 | 50 | TECMT | 1 | 48 | 343 | 608 |
| TECMR | 2 | 86 | 670 | 242 | ||
| CICT | 0 | 24 | 274 | 702 | ||
| CICR | 1 | 86 | 678 | 235 | ||
N - number of independent subjects
Ind - Independence; Exch - Exchangeable
TECM - ‘trace of the empirical covariance matrix’ criterion
CIC - ‘correlation information criterion’
T - No penalty: The criterion is based on Σ̂ that theoretically assumes correlation parameters are known
R - Penalty: The criterion is based on (Ip + Ĝ)Σ̂(Ip + Ĝ)T that realistically accounts for, or penalizes, covariance inflation due to correlation parameter estimation