ABSTRACT
When research is planned it is obviously important that as many factors as possible which
are not actually being studied but which might influence the results are controlled or
eliminated. For instance, if you are studying memory it would not be sensible to test
some people at 9 PM in a hot, noisy room and others at 9 AM in a peaceful, comfortable
setting. You would want to control factors-such as noise level and time of day-which
could affect people’s memory.
