无菌技术que refers to the actions of being "clean" in a lab environment. When working in a lab, one encounters many sensitive reagents, and any contamination or changes may affect your results drastically. In scientific research it is crucial that every result is dependable and more importantly: reproducable. If you cannot vouch for every ingredient and their concentration in a reaction mix, you cannot conclude anything based on those results. This is also the reason why most tests and measurements are done in triplets (three identical reaction tubes for each condition being tested). In that way, if similar results are obtained from all three samples, there is a greater chance that we can believe conclusions made from those results.