What is the value of performing a negative control test?

I just want to make sure..





is it so you know what the answer is not going to be, like what is not in the solution?





Please help! How would you describe the value of performing a negative control test?What is the value of performing a negative control test?
It can be to show that the materials you used were clean of contamination. As long as the negative control gives no response then all other positive responses can be taken as due to the independent reactant in the experiment.


In a PCR reaction- If the reagents have contaminating DNA then they carry a substrate that could give a false answer. A negative control experiment then sets up all the reagents and active catalysts but leaves out the critical independent variable the DNA being amplified. If there is any positive to this then the stocks were contaminated with foreign DNA and all results of the experiment are questionable.


A positive control would be to use a known strand of DNA to produce an expected answer. This shows the reagents are good in case the other answers are all negative. The experiment is still good it just had a negative answer.


All the other reactions would be with the unknown DNA samples being examined for yes/no answers.