Table 3 The parameter estimates, standard errors, t statistics and confidence level of different models of non-injury crashes, deaths and injuries on the Addis Ababa - Adama/Hawassa main road from 2002-2011
From: Effectiveness of an improved road safety policy in Ethiopia: an interrupted time series study
Models and variables | Coefficient | Standard error | tstatistics | Confidence interval |
|---|---|---|---|---|
Non-injury crashes: Prais- | Â | Â | Â | Â |
Winston regression (Model 1) | Â | Â | Â | Â |
 Intercept β0 | 295.1577 | 33.8195 | 8.73*** | (228.17, 362.14) |
 Baseline trend β1 | 3.248131 | .8461874 | 3.84*** | (1.57, 4.92) |
 Level change β2 | -40.19842 | 49.2873 | -.82 | (-137.81, 57.42) |
 Trend change β3 | -5.096253 | 1.538459 | -3.31** | (-8.14, -2.05) |
Death: Segmented regression (Model 2) | Â | Â | Â | Â |
 Intercept β0 | 150.1638 | 15.06675 | 9.97*** | (120.32, 1.10) |
 Baseline trend β1 | .3492265 | .3795861 | .92 | (-.40, 1.10) |
 Level change β2 | 3.599756 | 22.71791 | .16 | (-41.39, 48.59) |
 Trend change β3 | -1.961251 | .6828936 | -2.87** | (-3.31, -.60) |
Injuries: Segmented regression (Model 3) | Â | Â | Â | Â |
 Intercept β0 | 96.99802 | 22.13401 | 4.38*** | (53.16, 140.83) |
 Baseline trend β1 | 1.862395 | .557636 | 3.34** | (.75, 2.96) |
 Level change β2 | -43.5782 | 33.37405 | -1.31 | (-109.68, 22.52) |
 Trend change β3 | -1.489333 | 1.003214 | -1.48 | (-3.47, .49) |