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Fig. 1 | BMC Medical Research Methodology

Fig. 1

From: Comparison of six statistical methods for interrupted time series studies: empirical evaluation of 190 published series

Fig. 1

Graphical depiction of a segmented linear regression model fitted to ITS data. Secular trends (indicated by solid blue lines) for the pre and post interruption periods (indicated by the vertical dashed line) are estimated from the data (indicated by blue crosses). A counterfactual trend line (extrapolation of the pre-interruption trend line shown as a dashed blue line) is compared with the post interruption trend to estimate the immediate and longer term impact of the interruption. Model parameters are indicated as the intercept (\({\beta }_{0}\)); pre-interruption slope (\({\beta }_{1}\)); change in level at the interruption (\({\beta }_{2}\)), and the change in slope (\({\beta }_{3}\))

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