3.2b(ii) Confounding variables

Question 1

Confounding variables

Answer 1

Due to the complexities of biological systems, other variables besides the independent
variable may affect the dependent variable
These confounding variables must be held constant if possible, or at least monitored so
that their effect on the results can be accounted for in the analysis.

Question 2

Randomised blocks

Answer 2

When confounding variables cannot be easily controlled, randomised blocks are used.
Randomised blocks of treatment and control groups can be distributed in such a way that the influence of any confounding variable is likely to be same across the treatment and control groups.