layperson's judgment; amateur opinion
Refers to an opinion or decision made by someone without professional expertise, often implying it may be unreliable or naive.
Deciding on a difficult surgery based on a layperson's judgment is dangerous.
His advice is just an amateur opinion, so you should consult a specialist.
素人 means 'amateur' or 'layperson', while 素人判断 specifically refers to the judgment or opinion of such a person.
専門家 means 'expert' or 'specialist', the opposite of 素人. 素人判断 contrasts with expert judgment.
Compound of 素人 (しろうと, 'amateur, layperson') and 判断 (はんだん, 'judgment, decision').