Data Collection and Sampling

• What is a census?

  Measures every member of the population
• What is the advantage of a census?

  Accurate result
• What are the disadvantages of a census?

  • Time-consuming
  • Expensive
  • Testing may destroy
• What is a sampling unit?

  Individuals of a population
• What is a sampling frame?

  A list of all the individuals or units in a population from which a sample is drawn.
• What is simple random sampling?

  Individuals have the same chance of being selected
• How do we conduct a simple random sample?

  Use a random number generator or use lottery sampling
• What is the advantage of using simple random sampling?

  Lack of bias
• What is the disadvantage of using simple random sampling?

  Need sampling frame (not always possible)
• What is systematic sampling?

  Where every nth element in a population is selected to be part of the sample
• How do we calculate what every nth unit we use in systematic sampling?

  Population size / sample size
• How do we find out what number we start with in systematic sampling?

  Pick a random number between 1 and n (pop/sam)
• What is the advantage of using systematic sampling?

  Quick to use
• What is the disadvantage of using systematic sampling?

  Need sampling frame
• What is stratified sampling?

  Stratified sampling is a sampling technique where the population is divided into distinct strata, and a random sample is taken from each strata in proportion to its size.
• How do you find out how many individuals you sample in stratified sampling?

  Sample size / population size x size of strata for each strata
• What is the advantage of using stratified sampling?

  Reflects the population
• What is the disadvantage of using stratified sampling?

  Population must be classified in strata
• What are the random sampling techniques?

  • Simple random
  • Systematic
  • Stratified
• What are the non-random sampling techniques?

  • Opportunity
  • Quota
• What is quota sampling?

  Like stratified, but then recruit sample units until you reach your quota
• What is the advantage of using quota sampling?

  • No sampling frame
• What is the advantage of using quota sampling?

  Represents target population
• What is the disadvantge of using quota sampling?

  Risk of bias
• What is opportunity sampling?

  Participants are selected by those available at that time
• What is the advantage of using opportunity sampling?

  Easy, cheap and quick
• What is the disadvantage of using opportunity sampling?

  • Bias
  • Unlikely to be representative of the target population
• What are the two types of data?

  • Qualitative
  • Quantitative
• What are the two types of quantitative data?

  • Discrete
  • Continuous
• What is discrete data?

  Data that can only take on specific values
• What is continuous data?

  Data that can take on any value within a certain range.