It then requires statistics to determine if the two groups are different. Controls are an extremely important part of experimentation. There are several types of controls. Positive control - this is a control that should give a standard result. Negative control should not work.
Controls are the single most important aspect of biochemical experiments.
The proper controls can save weeks of time trying to interpret results that are caused by contamination, bad solutions or dead cells. Experiments often require development of techniques, or assays that take up a large part of the time in getting ready for an experiment. Sometimes the experiment itself talks only a matter of months, while developing the techniques can take a year prior to the actual experiment. In an introductory laboratory course we have tried our best to make the techniques work the first time, but often this is not possible. Techniques not working are just part of the everyday life of a scientists.