The antonyms for "are dubious" are words that express certainty and conviction. These words include confident, sure, convinced, certain, and definite. When you are confident about something, you do not have any doubts or hesitations regarding it. Being sure implies that you are completely certain about the truth or accuracy of something. If you are convinced, you have been persuaded or influenced to believe something with no doubts. Certain means that you have no doubt about the truth or certainty of something. On the other hand, definite means that something is clearly defined and established, without any doubts or uncertainties. All these words are antonyms for "are dubious" since they indicate certainty and conviction.