Sampling (Edexcel IGCSE Geography)

Types of sampling

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

• All sampling methods have advantages and disadvantages