Paper 3

• How did we use stratified sampling?

  It was used so that a safe, accessible site could be chosen at the upper course, middle course and lower course of Loughton Brook.
• Why was systematic sampling unsuitable

  Systematic sampling would be representative of the river, but some of the sites could have been inaccessible or unsafe.
• Why was random sampling unsuitable?


  random sampling, although unbiased, could have missed out one or two of the courses