In this video, we will discuss principles of experimental design and
learn some experimental design terminology.
The four principles of experimental design are control,
randomize, replicate, and block.
To control,means to compare treatment of interest to a control group.
To randomize, means randomly assigning subjects to treatments.
To replicate, means collecting a sufficiently large sample within the study
or to replicate the entire study.
The last principle of experimental design is blocking.
If there are variables that are know or suspected to effect the response variable,
first group the subjects into blocks based on these variables.
And then randomized cases with in each block to treatment groups.
Lets discuss blocking a bit more, we would like to design and
experiment to investigate if energy gels make you run faster.
The treatment group gets the energy gel,
the control group does not get any energy gel.
It is suspected that energy gels might effect pro and
amateur athletes differently therefore we block for pro status.
To do so, we divide our sample into pro and amateur athletes, and then,
we randomly assign pro and amateur athletes to treatment and
control groups, therefor, pro and amateur athletes are equally represented
in the resulting treatment and control groups.
This way, if we do find a difference in running speed between the treatment and
control groups we will be able to attribute it to the treatment,
the energy gel, and
can be assured that the difference isn't due to pro status since both pro and
amateur athletes were equally represented in the treatment and control groups.