Some correlations are perfect , as with the correlation between heating an iron rod and its expanding. There are no exceptions. Some correlations are statistical , as with the correlation between having fair skin and getting skin cancer. A is neither necessary nor sufficient for B, but A increases the probability that B will occur. Wet roads are not sufficient by themselves to bring about an accident, nor are they necessary for an accident to occur.
Wet roads do increase the chance of an accident, however.
In normal daily life we hardly ever have the kind of control we can have in scientific experimentation, but we are tempted to infer from correlations to causation in the same way. This leads to causal fallacies. Control Groups , to provide base rate information information about what we should expect with no experimental intervention in a situation. In daily life , people generally are prone to the Base Rate Fallacy forming conclusions based on information that has not been compared to base rate information. This is an example of the more general problem of dealing with information out of context .