Umm, when you watch the video Adey has linked to, you will understand the error, and it is one that is very commonly made by people.
Basically it comes down to this:
Correlation does not imply causality.
That is to say - the presence of two seemingly related variables doesn't always (or often) prove that one thing led to another.
You can read more about it here: http://en.wikipedia.org/wiki/Correlation_does_not_imply_causation
Better yet, just watch the video and you will understand medically and scientifically that the correlation of, for instance, autism and vaccination does not prove causality.
Umm, when you watch the video Adey has linked to, you will understand the error, and it is one that is very commonly made by people.
Basically it comes down to this:
Correlation does not imply causality.
That is to say - the presence of two seemingly related variables doesn't always (or often) prove that one thing led to another.
You can read more about it here:
http://en.wikipedia.org/wiki/Correlation_does_not_imply_causation
Better yet, just watch the video and you will understand medically and scientifically that the correlation of, for instance, autism and vaccination does not prove causality.