In a contested case the rules of evidence as applied in a nonjury civil case in circuit court shall be followed as far as practicable, but an agency may admit and give probative effect to evidence of a type commonly relied upon by reasonably prudent men in the conduct of their affairs. Irrelevant, immaterial or unduly repetitious evidence may be excluded. Effect shall be given to the rules of privilege recognized by law. Objections to offers of evidence may be made and shall be noted in the record. Subject to these requirements, an agency, for the purpose of expediting hearings and when the interests of the parties will not be substantially prejudiced thereby, may provide in a contested case or by rule for submission of all or part of the evidence in written form.