Biased or Unbiased Sample

1) Identify what the sample represents

A sample is a smaller group used to describe a larger population. The key question is whether the sample reflects the population fairly.

A sample is unbiased if every member of the population has a reasonable chance of being included, and the selection method does not favor one group over another. It is biased if the method systematically overrepresents or underrepresents part of the population.

2) Check the selection method

Ask:

1. Was the sample chosen randomly?
2. Was any group left out?
3. Did the method favor people who are easier to reach, more willing to respond, or more visible?

If the answer suggests unequal representation, the sample is biased.

3) Decide the final classification

• Unbiased sample: the selection process is fair and representative.
• Biased sample: the selection process is not fair or not representative.

When the exercise asks for a simplified final answer, give only the classification requested, such as biased or unbiased.

4) Quick check

A good test is to compare the sample to the population. If the sample would likely give a distorted picture of the whole group, it is biased. If it is likely to reflect the whole group accurately, it is unbiased.