Large-scale well-designed research studies have found either no association or only a small practically insignificant association between instructor gender and student ratings.
Li & Benton (2017) found no practically significant differences in mean ratings for 13,732 courses taught by female instructors (mean=4.19) and 11,511 courses taught by male instructors (mean=4.20) from across 256 Carnegie classification institutions and disciplines in the U.S. In STEM courses, women (mean=4.06; n=1,450) were rated slightly more highly than men (mean=4.03; n=2,483). However, this difference is practically insignificant.
Similar results were reported by Johnson et al (2013) who collected student ratings data from 3,938 courses taught at a large engineering college at a major U.S. public university. They found practically insignificant differences in the student ratings for male (mean=4.19, n=3394) and female (mean=4.13, n=544) instructors.
Centra & Gaubatz (2000), in a study of 741 U.S. courses across health sciences, business, education, social sciences, fine arts, natural sciences, technology, and humanities, found that female instructors did not receive significantly different overall ratings than male instructors by male and female students in any of the disciplines.
Please find below some references and further readings.
References and Further Readings:
Centra, J. A., & Gaubatz, N. B. (2000). Is there gender bias in student evaluations of teaching? The Journal of Higher Education, 71(1), 17–33. http://doi.org/10.1080/00221546.2000.11780814
Johnson, M. D., Narayanan, A., & Sawaya, W. J. (2013). Effects of course and instructor characteristics on student evaluation of teaching across a college of engineering. Journal of Engineering Education, 102(2), 289–318. http://doi.org/10.1002/jee.20013
Li, D., & Benton, S. L. (2017). IDEA Research Report #10: Is there gender bias in IDEA Student Ratings of Instruction? Manhattan, KS: The IDEA Center. https://www.ideaedu.org/Portals/0/Uploads/Documents/Research%20Reports/Research_Report_10.pdf
Ryalls, K., & Benton, S. L. (2016). IDEA Paper # 58: Challenging misconceptions about student ratings of instruction. Manhattan, KS: The IDEA Center. https://www.ideaedu.org/Portals/0/Uploads/Documents/IDEA%20Papers/IDEA%20Papers/PaperIDEA_58.pdf
Ryalls, K., Benton, S. L., Barr, J., & Li, D., (2016). IDEA Editorial Note #2: Response to “Bias Against Female Instructors”. Manhattan, KS: The IDEA Center. http://www.ideaedu.org/Portals/0/Uploads/Documents/Response_to_Bias_Against_Female_Instructors.pdf