Variation exists between members of a species. The need for random sampling, and the importance of chance in contributing to differences between samples.

Members of a species differ from each other (intra-specific variation).

We can use random sampling to analyse these differences.

This involves taking a small number of individuals at random from a population, analysing them, gaining statistics and then making the assumption that these statistics are the same for the whole population.

Normally this is carried out by having a grid of an area and using a random number generator to pick squares in the grid to analyse.

The benefit of random sampling is that there are multiple values put in so you get an average, reducing anomalies and making the result more representative, however because the figure is taken from just a sample, it means that you do not have to attempt to find a figure for every single individual.

Unfortunately there is an element of chance involved meaning that the statistics gained may be inaccurate as a non-representative sample was chosen. However, by increasing the sample size you can decrease the element of chance.