Societal stereotypes and biases pertaining to who belongs in physics and who can excel in it can impact motivational beliefs of women in physics courses. Prior research has shown that women have lower physics self-efficacy than men in physics courses in which women are underrepresented. However, prior research has generally not investigated similar issues in physics courses in which women make up the majority of students. This study examines self-efficacy of men and women with similar performance in introductory algebra-based physics courses in which women outnumber men at a large public research university in the US. These courses are taken primarily by biological science majors many of whom are interested in health professions. Although women are not underrepresented in these physics courses, societal stereotypes and biases internalized by female students over their lifetime can impact their self-efficacy when they take any physics course. We find a gender gap in self-efficacy disadvantaging women at the beginning of the course. However, unlike courses in which women are underrepresented, in which the self-efficacy gender gap often increases from the beginning to the end of the courses, we find that the self-efficacy gender gap for students who received a certain grade either remained constant or decreased somewhat. Moreover, except for the students who received an A grade, the average self-efficacy of most of the other student groups decreased from the beginning to the end of the semester. Additionally, we find that most of the self-efficacy gender gap is due to students' biased perceptions about their capability rather than the performance difference between women and men.