Friday, April 6, 2007

Difference between Simple Random Sampling and Convenience Sampling




Simple random sampling

A sampling procedure that assures that each element in the population has an equal chance of being selected is referred to as simple random sampling .

The selection bias is not possible in simple random selection.



In simple random selection the selection of units from the population does not based on easy availability it depends upon random selection.



The result can be generalize as the selection is done randomly.


Eg: An example may make this easier to understand. Imagine you want to carry out a survey of 100 voters in a small town with a population of 1,000 eligible voters. For example, we could write the names of all voters on a piece of paper, put all pieces of paper into a box and draw 100 tickets at random. You shake the box, draw a piece of paper and set it aside, shake again, draw another, set it aside, etc. until we had 100 slips of paper. These 100 form our sample. And this sample would be drawn through a simple random sampling procedure - at each draw, every name in the box had the same probability of being chosen.



Convenience Sampling


A convenience sample chooses the individuals that are easiest to reach or sampling that is done easy.


Convenience sampling does not represent the entire population so it is considered bias.


In convenience sampling, the selection of units from the population is based on easy availability and/or accessibility.



The results can not be generalize , the results are not applicable for all ,We can’t draw any meaningful conclusion from results we obtain.


Eg : If you want to choose 5 people from a class of 50. You could choose : First 5 students who. raise their hand. First 5 students in the first row. 5 tallest students .
A convenience sample is a sample where the students are selected, at the convenience of the researcher

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