a) In the first "empirical study of sexism in faculty hiring using actual faculty members",Cornell University researchers found that when using identical
qualifications, but changing the sex of the applicant, "women candidates
are favored 2 to 1 over men for tenure-track positions in the science, technology, engineering and math fields."
Here is a link to the study itself.
b) These conclusions generated reactions. Here is a link to an explanation of the many problems in the study mendioned in a). A major problem is that the conditions in the study were not at all like in real life. And there are many other problems. But you can follow the link and see for yourself.
c) Nown here is a study by several researchers from Yale which has been testing gender bias in applications which were much more comparable to actual academic hiring than the Cornell study (although for a slightly different group of fields and level of candidates)