Bias in sampling methods

Bias can be introduced by:

• relying on samples made up of volunteer respondents
• sampling from select groups within a population, without including the same proportion from all the groups in the population
• sampling from what is readily available
• selecting a sample that is too small in relation to the bigger population
• selecting a sample that is not generated randomly
• selecting a sample that is not representative of the bigger population.

Strategies to select samples need to take into consideration the purpose of the information. For example, when seeking information to help select equipment for a new gym, it may not be appropriate to ask members of the school band.