when the fact or phenomenon, instead of being recognized for what it is in reality, is mistaken for something else.
 John Stuart Mill, A System Of Logic, Ratiocinative And Inductive (1843). copy citation

Context

“It is non-observation, when all the error consists in overlooking, or neglecting, facts or particulars which ought to have been observed. It is mal-observation, when something is not simply unseen, but seen wrong; when the fact or phenomenon, instead of being recognized for what it is in reality, is mistaken for something else. § 2. Non-observation may either take place by overlooking instances, or by overlooking some of the circumstances of a given instance. If we were to conclude that a fortune-teller was a true prophet, from not adverting to the cases in which his predictions had been falsified by the event, this” source