Biostatistics : Sampling Method and Types of Sampling Methods

Sampling Method

• Sampling is simply the process of learning about the population on the basis of a sample drawn from it
• Two types of sampling methods

1) Random or probability samples 

2) Non random samples

1. Random Sampling

In this method every item in the universe has an equal chance of being selected
There are 3 types of random sampling methods
i)   Simple random sampling
ii)  Stratified sampling
iii) Cluster sampling

i) Simple random sampling

• In this method of sampling every unit of the population has an equal opportunity of being selected in the sample

ii)  Stratified sampling

• In this method of sampling a finite population is divided into certain strata or groups on the basis of certain characteristics

iii) Cluster sampling

• In this method of sampling the whole population divided into number of relatively small clusters or groups
• Then some of the clusters are randomly selected

2) Non random samples

• Non-random sampling methods are those which do not provide every item in the universe with a known chance of being included in the sample
• The selection process is partially subjective
• The choice of sample items depend upon the exclusively on the judgement of the investigater

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