Quanitative investigations of variation

Random sampling:

• Involves taking measurements of individuals selected from the population of organisms which is being investigated
• In theory, if these individuals can be representative of the whole population as a whole then the measurements can be relied upon

1. Divide the study area into a grid of numbered lines for example 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

Sampling bias -

• The selection may be biased
• The investigators may be making unrepresentative choices either deliberately or unwittingly

Chance -

• Even if sampling biased is avoided the individuals chosen may by pure chance not be representative

We can minimise the effects of chance by:

Using a large sample size -

• The more individuals that are selected the smaller the probability that chance will influence the result and the less influence anomalies will have

Analysis of the…