College students in online courses judge female instructors differently than male instructors, according to a recent study.

Researchers from North Carolina State University found that online students give higher marks to instructors they think they are men -- even when the professor is actually a woman.

"The ratings that students give instructors are really important, because they're used to guide higher education decisions related to hiring, promotions and tenure,"  Lillian MacNell, lead author of a paper on the work, said in a statement. "And if the results of these evaluations are inherently biased against women, we need to find ways to address that problem."

For the study, researchers evaluated a group of 43 students in an online course. The students were divided into four discussion groups of 8 to 12 students each. A female instructor led two of the groups, while a male instructor led the other two.

However, the female instructor told one of her online discussion groups that she was male, while the male instructor told one of his online groups that he was female. Because of the format of the online groups, students never saw or heard their instructor.

At the end of the course, students were asked to rate the discussion group instructors on 12 different traits, covering characteristics related to their effectiveness and interpersonal skills.

Researchers found that students who thought they were being taught by women gave lower evaluation scores than students who thought they were being taught by men. It didn't matter who was actually teaching them. The instructor that students thought was a man received markedly higher ratings on professionalism, fairness, respectfulness, giving praise, enthusiasm and promptness.

"We found that the instructor whom students thought was male received higher ratings on all 12 traits, regardless of whether the instructor was actually male or female," MacNell said. "There was no difference between the ratings of the actual male and female instructors."

Researchers hope to expand this approach to additional courses, and different types of courses, to determine the size of this effect and whether it varies across disciplines.

The findings are detailed in the journal Innovative Higher Education.