2 ms·
Could you elaborate? Which confounding variables?
by djf1 12y ago
Could you elaborate? Which confounding variables?
- CamperBob2 12y agoEverything else that changed over the course of the study period. Speed limits might have been lowered, enforcement patterns might have been revised, the congestion charges might have changed, the weather might have been different. It would be more helpful to see a graph showing historical trends stretching back at least ten or twelve years, just to give us an idea of the standard deviation.