Identify biased samples

key notes :

In a biased sample, some people or items are more likely to be chosen than others.

Learn with an example

➡️ Adriana bought 2 eggs from each farmer at the farmers’ market. Each farmer had an equal number of eggs.

Is this sample of the eggs at the farmers’ market likely to be biased?

  • yes
  • no

Since Adriana divided the eggs into equal-sized groups by farmer and then chose an equal number of eggs from each farmer, it is a representative sample. It is not likely to be a biased sample.

➡️ For a statistics project, Emilio distributed a questionnaire and asked his classmates to fill it out. 2 of them did.

Is this sample of the students in the class likely to be biased?

  • yes
  • no

Since the students who chose to fill out the questionnaire might not be similar to the students who did not choose to fill it out, it is likely to be a biased sample.

➡️ Christina polled 87 people at the town senior centre.

Is this sample of residents of the town likely to be biased?

  • yes
  • no

Since people at the senior centre might not be similar to the other residents of the town, it is likely to be a biased sample.

let’s practice!