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| BS1.1: Population and Sample |
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| BS1.1: Population and Sample |
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OBJECTIVES |
| At the end of this section you should be able to understand the concept of "population" and "sample". |
The study population is the entire group of individuals having certain common characteristics about which statistical inferences can be made. The population must be clearly defined in terms of any characteristics relevant to the study.
Usually it is not possible to study the entire population as this would take too much time and waste limited resources. It is therefore necessary to consider a sample and to relate its characteristics to the total population. However, the sample selected must reflect the population, and is dependent on the way the sample is selected.
A random sample is one in which each individual in the population has an equal chance of being selected. One way of selecting a random sample is to use a table of random numbers. Random numbers may also be generated by a computer program or drawn from a hat.
The study population for a descriptive study to determine the blood lead concentration among males exposed to lead might be "all male workers in Cape Town exposed to lead in battery manufacturing plants".
The sample might be 25 battery manufacturing plant workers exposed to lead, where each individual is chosen entirely by chance.
