Social influence or pressure on scientists is external but what about influence from within? It has been known for quite a while that the beliefs and attitudes of the people conducting the experiments affect the results they achieve.
For instance an experimenter may inadvertently treat the experimental groups differently. Also observers coding data or events may unconsciously let bias creep into their scoring. When scientists make mistakes in calculations that fall in with their prediction or hypothesis they are much less likely to notice them than when the mistake stands out against the direction of the hypothesis.
Scientists are under great pressure, putting themselves and their procedures under the microscope in order to remain objective. That means putting their emotions and feelings about their research to one side and conducting their experiments as if they were indifferent to the outcome.
Karl Popper pointed out that, the only way a scientist could be sure that he or she was not influencing their results in their desire to prove a theory, was to always work to prove the theory wrong – “Every genuine test of a theory is an attempt to falsify it, or to refute it.” If the theory is robust then it will beat such challenges.
Another way to beat the experimenter effect is to make sure the people conducting the experiment don’t know what drugs they are administering or which chemicals they are testing. This is called a double blind. Neither the experimenter nor the participants know what to expect.
Understanding the maths