factors to achieve a representative sample

factors to achieve a representative sample

1. location of samples

   • random
     • areas with a regular shape
     • coordinates randomly generated
   • systematic
     • samples taken at regular intervals

2. number of samples

   • preliminary study
     • finding an estimate on how many samples to take
   • enough samples to eliminate the effect of variability

3. size of samples

   • large
     • more accurately representative
     • reduces the effect of anomalies
   • small
     • take less time

4. standardised techniques

   • all must be collected in exactly the same way
   • allows for comparison across researchers
   • other variables which could affect results must be controlled

5. timing of samples

   • identify changing trends
   • for variables which change over time
   • sampled again on different occasions to produce mean results and understand trends