PRAC RES lesson 10

• Sampling


  The process of selecting the individual units for study in a research project
• Population


  The bigger group from where you choose the sample
• Sampling frame


  The list of the members of the population from where you will get the sample

  
• Probability sampling or unbiased sampling


  Involves all members listed in the sampling frame representing a certain population, with an equal chance of participation in the sampling or selection process

  
• Sampling error crops up if the selection does not take place in the way it is planned. Such sampling error is manifested by strong dissimilarity between the sample and the ones listed in the sampling frame.

  
• Sampling error


  The number of sampling errors depends on the size of the sample - the smaller the sample, the bigger the number of sampling errors

  
• The right sample size depends on whether the group is heterogeneous or homogeneous - a heterogeneous group requires a bigger size, a homogeneous group requires a smaller one
• Simple random sampling


  1. Have a list of all members, write each name on a card, and choose cards through a pure-chance selection

  2. Have a list of all members, give a number to each member and then use randomized or unordered numbers in selecting names from the list
• Systematic sampling


  Choose a set of numbers like 1 to 15, and out of a list of 1,500 students, take every 15th name on the list until you complete the total number of respondents to constitute your sample

  
• Stratified sampling


  The group comprising the sample is chosen in a way that such group is liable to subdivision during the data analysis stage

  
• Cluster sampling


  Isolate a set of persons instead of individual members to serve as sample members, e.g. randomly select three sections with 40 students each to constitute the sample

  
• Non-probability sampling


  Disregards random selection of subjects, the subjects are chosen based on their availability or the purpose of the study, and in some cases, on the sole discretion of the researcher

  
• Quota sampling


  Choose sample members possessing or indicating the characteristics of the target population
• Voluntary sampling


  The subjects you expect to participate in the sample selection are the ones volunteering to constitute the sample
• Purposive or judgmental sampling


  Choose people whom you are sure could correspond to the objectives of your study, like selecting those with rich experience or interest in your study
• Availability or convenience sampling


  The willingness of a person as your subject to interact with you counts a lot, you automatically consider them as your respondents
• Snowball sampling


  Does not give a specific set of samples, you tend to increase the number of people you want to form the sample of your study
• SIMPLE RANDOM SAMPLING


  using a pure-chance selection, you assume every member has the same opportunity to be in the sample
• STRATIFIED RANDOM SAMPLING


  involves the division of a population into smaller sub-groups known as STRATA.

  • segregating people
  • same qualities and characteristics
• SYSTEMATIC SAMPLING


  members from a larger population are selected according to a random starting point but with a fixed, periodic interval.

  • example, one seat apart ang pagpick ng respondents
• CLUSTER RANDOM SAMPLING


  used when there are different subsets if groups present in a large population

  • dont share similar qualities but grouped just because
  • example, the boat is sinking
• CONVENIENCE SAMPLING


  often geographically close to the researchers.

  leverage individuals that can be identified and approached with as little time as possible.
• QUOTA SAMPLING


  gathering representative data from a group. this sampling requires that representative individuals are choses out of a specific sub-group.

  • it identifies the number of respondents
  • meets a quota
• JUDGMENT OR PURPOSIVE SAMPLING


  rely on their judgment when choosing members of the population to participate in their study.

  • look at one quality
• SNOWBALL SAMPLING


  research participants recruit other participants for a test or study. It is used where potential participants are hard to find

  • referral sampling
• VOLUNTARY SAMPLING


  researcher puts out request for members of a population to join the sample

  • the people decide whether to be in the sample or not.