Table 3.

Comparison of Expected Values for Factor Loadings in a Linear Growth Model and Observed Values in the Full Latent Growth Model of Change in Posttraumatic Stress Disorder (PTSD) Symptoms During 28 Days of Cocaine and Alcohol Abstinence

Number of Days of Abstinence	Expected Value (Linear Growth Model)	Observed Value (Full Latent Growth Model)
2 days	0/26 = 0.0	0.0 (fixed)
5 days	3/26 = .115	.235
10 days	8/26 = .308	.467
14 days	12/26 = .462	.806
21 days	19/26 = .731	.996
28 days	26/26 = 1.00	1.00 (fixed)

Note: Expected Values for factor loadings range from 0.0 to 1.0 and represent the proportion of change in PTSD symptoms expected to have occurred at each time point if change were linear across time (e.g., .115 = 11.5% of total change). The period between the first assessment (2 days of abstinence) and the final assessment (28 days of abstinence) is 26 days, so the proportion of change expected in a linear model is calculated as number of days elapsed divided by 26 days. Similarly, the initial (2 days) and final (28 days) factor loadings for the growth factor in the Full Latent Growth Model were fixed at 0.0 and 1.0 to set the metric for the growth factor as the proportion of change in PTSD symptoms observed to occur across the 26 day measurement period.