Table 2.
Variability in average activity counts before and after intervention (N = 30).
| Covariance parameter estimates | Subject | B | Std. error | Z | p |
|---|---|---|---|---|---|
| Random effects: prediction of activity variability | |||||
| Intercept | ID | 1331.66 | 466.52 | 2.85 | <.01 |
| Residual | ID | 498.50 | 157.53 | 3.16 | <.01 |
|
| |||||
| Predictor variables and control variables | β | Std. error | DF | t | p |
|
| |||||
| Fixed effects | |||||
| Intercept | 26.64 | 23.63 | 28 | 1.13 | .27 |
| Average activity counts per minute (level 1) | 0.35 | 0.06 | 21 | 5.87 | <.01 |
| Time (baseline = 0, follow-up = 1) (level 1) | 21.72 | 9.44 | 21 | 2.30 | .03 |
| Group (general = 0, tailored = 1) (level 2) | −20.60 | 15.71 | 28 | −1.31 | .20 |
| Time × Group (level1 × level2) | −37.25 | 12.84 | 21 | −2.90 | <.01 |
Note. In examining the distribution of the standard deviation of activity level, we observed a tendency toward a slight positive skew (1.54) and some kurtosis (2.70). These tendencies were substantially reduced by transforming this variable by taking its square root. However, doing so did not significantly alter any of the central findings, so for ease of interpretation, we present only the non-transformed variable.