Sampling (Edexcel IGCSE Geography)

Types of sampling

Spec point — SX.007

Purpose of sampling

• It gives an overview of the whole feature/population to be sampled
• There is not enough time/equipment/access to measure the whole area being examined
• Sampling provides a representative and statistically valid sample of the whole

Types of sampling

• There are three types of sampling to consider

  • Random
  • Systematic
  • Stratified

• Random sampling

  • A grid is drawn/placed over the area to be studied
  • The squares which include part of the study area are numbered
  • The numbers are entered into a random number generator
  • The samples should be collected as near as possible to the points given

• Systematic sampling

  • The samples are selected at regular intervals for example every 500 meters or every tenth person

• Stratified sampling

  • Used when the study area includes significantly different parts known as subsets
  • Is based on the idea that the sample represents the whole population
  • If a questionnaire is being used to collect data and the population of the study area has 10% of people over 65, then the sample should include 10% of people over 65

• Where the sample site cannot be accessed opportunistic sampling can be used

  • The site used should be as close as possible to the inaccessible sample site

• All sampling methods have advantages and disadvantages

Random sampling advantages and disadvantages

Systematic sampling advantages and disadvantages

Stratified sampling advantages and disadvantages