2

• Practical Research 1 Quarter 4 Week 2
• Topic: Sampling Procedures
• Sampling


  The act or process of selecting pre-determined items (e.g. individuals, organization etc.) from a large population for measurement or analysis
• Sample


  A subset (selected elements) of a population that is used to represent the entire population
• The sample should be representative of the population to ensure that we can generalize the findings from the research sample to the population
• Qualitative sampling


  • The primary goal is to get a representative sample, or a small collection of units or cases from a much larger collection or population, such that the researcher can study the smaller group and produce accurate generalizations about a larger group
  • Qualitative researchers focus on how the sample or small collection of cases, units, or activities illuminates key features of social life
  • The purpose of sampling is to collect cases, events, or actions that clarify and deepen understanding
• Sampling procedures/methodologies/techniques


  • Probability sampling
  • Non-probability sampling
• Non-probability sampling


  A sampling technique in which the researcher selects samples based on the subjective judgment of the researcher rather than random selection
• When to use non-probability sampling


  • To indicate if a particular trait or characteristic exists in a population
  • When conducting qualitative research, pilot studies, or exploratory research
  • When the researcher has limited time or budget constraints
  • When the researcher needs to observe whether a particular issue needs in-depth analysis
  • When the researcher does not intend to generate results that will generalize the entire population
• Types of non-probability sampling

  • Convenience sampling
  • Purposive/Judgemental sampling
  • Quota sampling
  • Snowball sampling
• Probability sampling


  A sampling technique wherein the researcher uses a method based on probability theory to select samples from a larger population
• For a participant to be considered as a probability sample, he/she must be selected using a random selection
• Sampling of probability assumes that each member of a population has a known and equal chance of being chosen
• Types of probability sampling

  • Simple random sampling
  • Stratified random sampling
  • Cluster random sampling
  • Systematic sampling
• Simple random sampling


  • An inherently random way of choosing items
  • The sample contains those representatives whose numbers are selected
• Stratified random sampling


  • Involves the division of subjects into groups which are mutually exclusive and then the use of basic random sampling to pick group members
• Cluster random sampling


  • A way to randomly select participants from a list that is too large for simple random sampling
• Systematic sampling


  • Choosing every "nth" participant from a complete list
• Advantages of probability sampling

  • Cluster sampling: convenience and ease of use
  • Simple random sampling: creates samples that are highly representative of the population
  • Stratified random sampling: creates strata or layers that are highly representative of strata or layers in the population
  • Systematic sampling: creates samples that are highly representative of the population, without the need for a random number generator
• Disadvantages of probability sampling

  • Cluster sampling: might not work well if unit members are not homogeneous (i.e. if they are different from each other)
  • Simple random sampling: tedious and time consuming, especially when creating larger samples
  • Stratified random sampling: tedious and time consuming, especially when creating larger samples
  • Systematic sampling: not as random as simple random sampling
• Stratified random sampling


  Creates strata or layers that are highly representative of strata or layers in the population
• Systematic sampling


  Creates samples that are highly representative of the population, without the need for a random number generator
• Cluster sampling


  • Might not work well if unit members are not homogeneous (i.e. if they are different from each other)
• Simple random sampling


  • Tedious and time consuming, especially when creating larger samples
• Stratified random sampling


  • Tedious and time consuming, especially when creating larger samples
• Systematic sampling


  • Not as random as simple random sampling
• Types of Probability Sampling

  • Stratified random sampling
  • Systematic sampling
  • Cluster sampling
  • Simple random sampling
• When a sample of 6 numbers is randomly generated from a population of 49, each number has an equal chance of being selected and each combination of 6 numbers has the same chance of being the winning combination
• Systematic sampling


  • A radio advertiser wishes to choose a random sample of size 100 from a population of 5,000 listeners. After observing that 5,000÷50 = 100, he first selects a subject at random from the first 50 names in the sampling frame, and then he selects every 50th subject listed after that one
• Stratified random sampling


  • The radio advertiser divides the population into five separate groups and then selects a simple random sample from each group
• Cluster sampling


  • The radio advertiser divides the population into a large number of groups. He selects a simple random sample of the groups and then surveys every subject in each of the groups selected
• An airline offers a certain flight once per day that usually contains about 25 passengers


  The airline wants to survey 500 passengers of this flight about their overall satisfaction. The passengers will be selected using a cluster random sample where each flight is a cluster
• Contacting all the passengers on a few flights will probably be more efficient than contacting passengers spread out across many flights
• A cluster sample chooses some passengers from each flight, so the airline will be more likely to get a representative sample
• Convenience sampling


  • Choosing for my sample whoever walks by in the mall
• Snowball sampling


  • Recruiting for my sample my friend Joe, and he recruits his friend Amber, and she recruits her friend Gina
• Quota sampling


  • Recruiting participants based on age and gender
• To use samples to estimate something from the population, the sample should be representative of the population