Control
A control is an experiment in which the hypothesised variation does not occur
- so the hypothesised effect should not occur either
e.g. Macaque monkeys given vaccine based on human T-cells infected with SIV (relative of HIV)
- macaques gained immunity from SIV
Later, macaques given uninfected human T-cells
- and macaques still gained immunity!
Control experiment not originally done
- and not always obvious (you can’t control for all variables)