What is undercoverage bias?

Undercoverage bias refers to a type of bias that occurs when certain individuals or groups in a population are systematically excluded from a sample in a survey or study. This can lead to inaccurate or misleading results because the sample may not be representative of the broader population.

One common source of undercoverage bias is non-response bias, where certain individuals do not participate in a survey or study. This can occur for various reasons, such as lack of interest, inability to participate, or refusal to participate. If those who do not respond to the survey differ systematically from those who do, the sample may not be representative of the population.

Another source of undercoverage bias is sampling bias, which occurs when the sampling method used does not give all members of the population an equal chance of being included in the sample. For example, if a survey is conducted via telephone and only includes individuals with landline phones, those who only have cell phones may be underrepresented in the sample.

To address undercoverage bias, researchers can try to improve response rates by using appropriate survey methods, such as offering incentives or using multiple modes of data collection. They can also use weighting techniques to adjust for differences between the sample and the population. Ultimately, being aware of potential undercoverage bias and taking steps to mitigate it can help ensure the validity and reliability of research findings.