Veterinary Epidemiology and Zoonosis

TYPES OF SAMPLING

The types of sampling are,

•  Non-probability sampling
•  Probability sampling

Non-probability sampling

• In which the choice of the sample is left to the investigator.
• Convenience sampling
  • It is the collection of easily accessible sampling units.
  • Example: If we want to collect faecal samples in the forest to screen the wild animals to know the status / prevalence of parasitic diseases, collecting samples near by entrance area (not sampling around the forest area).
    • Selecting first 15 animals (sampling units) from the study population (or list of 150 animals in the study population).
• Purposive or Judgmental sampling
  • It is the choice of a sample, the averages of whose quantitative characteristics (example body weight) or distribution of whose qualitative characteristics (examples are sex and breed) are similar to that of the target population.
  • The objective is to select a sample where characteristics are balanced with those of the target population.

Disadvantages

• Sampling by convenience
• Sample is not a true representative
• Biased estimates