While the inspection of various software artifacts increases the quality of the end product, the effectiveness of an inspection depends largely on the individual inspectors involved. To address that issue, a large-scale controlled inspection experiment with over 70 professionals was conducted at Microsoft Corporation that focused on the relationship between an inspector's background and their effectiveness during a requirements inspection. The results of the study showed that inspectors with university degrees in majors not related to computer science found significantly more defects than those with degrees in computer science majors. We also observed that level of education (Masters, PhD), prior industrial experience or other job related experiences did not significantly impact the effectiveness of an inspector. The only other type of experience that had a significant impact on effectiveness was experience in writing requirements, i.e. professionals with prior experience writing requirements found statistically significant more defects than their counterparts.