Is there a scientific causal link to back up the apparent statistical relationship?
It is incorrect to assume causality from a statistical relationship. To illustrate this, take the assertion that wearing a baseball cap backwards is linked to a 20 point reduction in the IQ score of the wearer. A plausible statistical link. It would be obviously ridiculous to suggest that educational standards could be increased at a stroke by banning baseball caps unless it could be proven that the cap was the cause of the low intelligence rather than simply a symptom. If the ban went ahead anyway, the real causes of low achievement in school would be ignored and some rather more intelligent people would get sunstroke due being forced to venture into the midday desert sun hatless. A ludicrous scenario? It is not far from what has been done to the motorist here! • Is the sample representative? It has been assumed that because a graph neatly fits these six examples then the same must be true of all roads. To be valid, a survey must be chosen at random from a representative section of th
