| Interspecific variation | - If 1 species differs from another |
| Variation | - Differences between individuals
- Can be caused by genetic or environmental factors or a combination |
| Intraspecific variation | - Members of the same species differing from each other |
| What influences results | - Sampling bias
- Chance
- Large sample size
- Analysis of the data collected |
| Sampling bias | - Selection may be biased
- The investigators may be making unrepresented choices either deliberately or unwittingly |
| Best way to prevent sampling bias | - Random sampling |
| Random sampling method | - Mark up a grid on a map of the study area
- Label the grid with coordinates
- Use a random number generator to choose a set of coordinates |
| Chance | - Even if sampling bias is avoided, individuals chosen may, by pure chance, not be representative |
| Using large sample size | - The more individuals that are selected the smaller the probability that chance will influence the result
- So the less influence anomalies will have |
| Analysis of the data collected | - Accepting that chance will play a part, the data can be analysed using statistical tests
- To see how much chance may have influenced the data or any other cause |
| Standard deviation | - A measure of the width of the curve
- Shows us the spread of data around the mean |
| Calculating standard deviation | SD = √Σ (x - X̄)²/n-1
Σ = sum of
x = measured value (from sample)
X̄ = mean value
n = total no. of values in the sample |
