Veterinary Epidemiology and Zoonosis

SIMPLE RANDOM SAMPLING AND SYSTEMATIC SAMPLING

Simple random sampling 

• Selection of sample is by drawing up from a list of animals in the study population (in which each sample is having equal chance of being selected by luck).
  • Eample: If 20 cows to be selected to analyse the quantity and quality of milk production in a herd of 200 cows (study population).
• Code for every cow would be written on the identical sheet and then picking up a sample (cow) randomly.

Systematic sampling

• The first animal is being selected randomly from the proportionate level of the study population and then selection of sampling units at equal intervals.
  • Example: If one animal in every 10 animals is required, then the first animal would be selected randomly from the first 10.
• If it is 4^th animal, then the samples would be 14, 24, 34, 44 and so on.

S.No	Simple	Systematic
1	It requires total knowledge about the study population	Only for the proportionate size of the study population to select the first sample randomly
2	All the animals in the study population should be identified	Not necessary to identify all the animals
3	Samples drawn may not be evenly spread	Evenly spread in the study population
4	Comparatively difficult method	Relatively easy method