(4) Sampling Procedure and the Sample

• population - the totality of all the objects, elements, persons, and characteristics under consideration
• population - it is understood that this population possesses common characteristics about which the research aims to explore
• two types of population

  1. target population
  2. accessible population
• actual population - the target population
• accessible population - the portion of the population in which the researcher has reasonable access
• sample - when the population is too costly or time-consuming or impractical to consider, a representative is identified
• sampling - pertains to the systematic process of selecting the group to be analyzed in the research study
• sample - the goal is to get information from a group that represents the target population
• a good sample should have characteristics of the represented population- characteristics that are within the scope of the study with fair accuracy
• approaches in identifying the sample size:

  1. heuristics
  2. literature review
  3. formulas
  4. power analysis
• heuristics - this approach refers to the rule of thumb for sample size
• research design [no.of subjects/participants]

  descriptive - 10% to 20%

  comparative research - 15 subjects/ groups

  survey- 800

  correlational- 100-200

  ex post facto - 30+

  experimental - 30/more
• literature review - this approach is by reading similar/ related literature and studies to your current research study. Using this approach increases the validity of your sampling procedure.
• formulas - being established for the computation of an acceptable sample size. The common one is Slovin's Formula.
• Slovin's Formula - n=N/1+Ne^2
• power analysis - this approach is founded on the principle of power analysis. There are two principles you need to consider if you are going to use this approach: statistical power and effect size.
• statistical power - the probability of rejecting the null hypothesis.
• statistical power - it suggest that there is a relationship between the independent and dependent variables of the research study.
• statistical power - It will be used to identify the sufficient sample size for measuring the effect size of a certain treatment.
• effect size - the level of difference between the experimental group and the control group
• if the statistical power tells that relationship between independent and dependent variables, the effect size suggests the extent of the relationship between these two variables.
• once a good sample is obtained, the generalizability and applicability of findings increase