Veterinary Epidemiology and Zoonosis

OBJECTIVES OF SAMPLING AND NATURE OF SAMPLING UNITS

Objectives of sampling

• It is to provide an unbiased estimate of the variables that is being measured in the population.
• Biased estimates would be produced when list of members of the frame are incomplete, information is obsolescent, segments of the frame are untraceable, there is a lack of co-operation by some members of the frame and sampling procedures are not random.
• The sources of bias are non-compensatory errors because they cannot be reduced by increasing the size of the sample.

Nature of sampling units

• It may be individual animals or aggregates such as herd, farm.