Walmart's decision to sample only stores in the Western states leads to what type of sampling bias?

Sampling only stores in the Western states introduces undercoverage because it fails to include stores from other regions that may have different characteristics and customer behaviors. Undercoverage occurs when certain groups within the population being studied are not adequately represented in the sample. In Walmart's case, by excluding stores outside the Western states, the data collected may not truly reflect the entire company's performance or customer preferences across all geographical areas.

This can lead to skewed results and conclusions that may not be applicable to the broader population of Walmart stores. The insights gained from just a subset of stores may overlook important differences that exist in other regions, which could result in misleading business decisions based on incomplete data.

Sampling bias is a related but distinct concept that refers more broadly to systematic errors introduced into a sample selection process. Here, since the bias specifically arises from not including stores from other regions, undercoverage is the more precise term to describe the issue at hand.