Exhibit 23(b) CONSENT OF ENGINEER We hereby consent to the incorporation by reference in this Post-Effective Amendment No. 1 to the registration statement on Form S-8 filed by MDU Resources Group, Inc. with the Securities and Exchange Commission on October 29, 1992 (Registration No. 33- 53896) of our estimates, dated January 10 and 31, 1995, which appear in or are incorporated by reference in the MDU Resources Group, Inc. Annual Report on Form 10-K for the year ended December 31, 1994. RALPH E. DAVIS ASSOCIATES, INC. /s/ Joseph Mustacchia Jr. Executive Vice President October 12, 1995 Houston, Texas