INTERSPECIFIC VARIATION - when one species differs from another.
INTRASPECIFIC VARIATION - when members of the same species differ from one another.
SAMPLING - not all measurements can be classed as representative:
Sampling Bias - The selection process may be biased, investigators may be making unrepresentative choices, deliberately or unwittingly.
Chance - Even if sampling bias is avoided, the individuals chosen, may be by pure chance, unrepresentative.
To reduce sample bias, random sampling is carried out:
1. Divide the study area into a grid of numbered lines, e.g by stretching two long tape measures at right angles to each other.
2. Using random numbers, from a table or generated by a computer, obtain a series of coordinates.
3. Take samples at the intersection of each pair of coordinates.
To minimise the effects of chance:
Large Sample Size…