Sampling

• Sampling

  The process of choosing the representative portion of a population
• If a firm increases advertising, their demand curve shifts right, increasing the equilibrium price and quantity
• Population


  The totality of all values (or measurements) of a particular characteristic for a specified group of objects that are of interest to the researcher
• Types of Sampling Design

  • Scientific sampling
  • Non-scientific sampling
• Experimentation is being conducted to investigate a population that has been altered for study
• Unrestricted random sampling allows every member in the population an equal chance of inclusion in the sample
• Multistage Sampling


  Done in several stages, such as two-stage, three-stage, four-stage, five-stage, depending on the number of samplings to be used
• Stratified Random Sampling

  Divides the population into two or more strata, and sample items are drawn at random for each stratum
• Sample


  A finite portion of a population that will be used or investigated in the study
• Experimentation

  Study the effect that a change in one variable (independent variable) has on another variable (dependent variable)
• Reasons for sampling

  • Due to limitations of time, money, or personnel
  • Examining an item may require that the item be destroyed
  • Samples due to their small size can be thoroughly studied
  • Fewer errors are encountered in the collection and handling of data
  • The study of a larger or more varied population can be carried out at a lesser cost
• Systematic Sampling


  Individuals in the population are arranged in a methodical manner, and the nth name may be selected in the construction of the sample
• Random sampling can be chosen using the lottery or table of random numbers techniques
• An experimental design cannot be carried out unless one knows how to do sampling
• Restricted random sampling is applicable only when the population being investigated is homogeneous and likely to arrive at accurate values of the population characteristics
• Marginal utility

  The additional utility (satisfaction) gained from the consumption of an additional product. Total utility is the sum of marginal utilities for each unit
• Cluster Sampling


  Population is grouped into clusters or small units
• Multistage Sampling

  Population individuals are grouped hierarchically, and sampling is done consecutively
• Quota Sampling


  Main office prepares the sampling technique with instructions to gather data from samples that meet prescribed criteria or characteristics
• Purposive Sampling


  An individual is selected as part of the sample due to good evidence that he is a representative of the total population
• Advantages of Sampling

  • It saves time, money, and effort
  • It is more effective
  • It is faster, cheaper, and economical
  • It is more accurate
  • It gives more comprehensive information
• Disadvantages of Sampling

  • Sample data involve more care in preparing detailed subclassification due to small number of subjects
  • If the sampling plan is not correctly designed and followed, the result may be misleading
  • Sampling requires an expert to conduct the study in an area, if lacking, the results can be erroneous
  • The characteristics to be observed may occur rarely in a population, for instance, teachers over 30 years of teaching experience or teachers with outstanding performance
  • Complicated sampling plans are laborious to prepare
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• Multistage Sampling


  • Nationwide study: regions chosen as the first stage, provinces as the second stage, municipalities as the third stage, barangay as the fourth stage
• Cluster Sampling


  • Blocks or districts in a municipality or city composed of population individuals
• Advantages of Sampling
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• Incidental Sampling


  The investigator simply takes the nearest individuals as subjects of the study until the sample reaches the desired size
• Disadvantages of Sampling