There have been studies that have contradicted the 10,000 hour rule. However, my understanding is that the rule is about attaining mastery through effective pr

There have been studies that have contradicted the 10,000 hour rule. However, my understanding is that the rule is about attaining mastery through effective practice. You don't need to reach mastery level in order to be make a valuable contribution in a new job. Obviously it really depends on what sort of career change you are contemplating. If it is to become an international concert pianist and you have never studied music or played any musical instrument, then it is most likely a stretch goal. However, if you are a competent programmer with one language or environment, then changing to a different language, etc will probably see you being quite good after a year, i.e. 2000 hours. With more effort you can only improve.