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How to Select Representative Samples

Life and social scientists study observations or behavior to explain why something happens. A population is any defined group of members, units or observations that a researcher studies. For example, you may wish to study all female voters in Texas. A sample is simply a subset or a part of the population. Researchers perform statistical analyses on samples to draw conclusions, or answer questions, about the whole population. For these conclusions to be valid, the sample must be representative, which means it must approximately mirror the characteristics found in the population.

Data set

Instructions

- 1
  Define the population. Identify exactly who or what you are studying, such as all wheat farmers in Kansas or American history books in the New York Public Library.
- 2
  Assign a unique identification number to each member of the population. If you have a population of 1,000 Kansas wheat farmers, you could randomly assign each farmer a number between 1 and 1,000.
- 3
  Pick your sample cases from the population randomly. Each member of the population should have an equal chance of being selected. Randomly choose a specific member of the population.
- 4
  Select each additional case based on a predetermined interval. For example, you could begin with farmer number 15 in the population of Kansas wheat farmers. Then you could choose each 20th farmer after number 15.
- 5
  Choose sample units from the population until you reach the total number of cases needed for your sample.

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