Table 3

Coefficients estimated from interrupted time series analysis models

DescriptionCoefficient (95% CI)
A: Data not controlled for seasonality
β0: starting level (baseline) of availability63.08 (61.29 to 64.88)**
β1: the trajectory of availability until the introduction of the intervention0.03 (−0.08 to 0.14)
β2: the change in the level of availability in the period immediately following the introduction of the intervention (compared with the counterfactual)12.58 (9.56 to 15.60)**
β3: the difference between preintervention and postintervention slopes of availability0.17 (0.02 to 0.32)*
β1 + β3: the postintervention linear trend of availability0.2 (0.09 to 0.31)*
B: Data controlled for seasonality using a cubic spline
β0: starting level (baseline) of availability62.17 (59.48 to 64.85)**
β1: the trajectory of availability until the introduction of the intervention0.14 (−0.08 to 0.37)
β2: the change in the level of availability in the period immediately following the introduction of the intervention (compared with the counterfactual)9.69 (4.75 to 14.62)**
β3: the difference between preintervention and postintervention slopes of availability0.10 (−0.13 to 0.32)
β1 + β3: the postintervention linear trend of availability0.24 (0.13 to 0.35)**
  • *P<0.05, **P<0.01.