Investigating Variation

• Sampling Bias: Process may be bias as investigators may make unrepresentative choices, e.g. taking surveys from one area rather than another due to an unfavourable cause (for example, too many nettles to walk through, or covered in cow dung.)
• Chance: Process may result in the individuals, by chance, being unrepresentative, e.g. indiviuals are of a better quality than rest of a population.

Random Sampling:

1. Divide study area using a grid of numbered lines. 

2. Use random numbers to generate a series of coordinates.

3. Take samples at the intersection.

How to remove chance:

• Use a larger sample size (reduces probability that chance will affect result).
• Analyse data collected (use statistics to take into account influence of chance).