Question

When a researcher assigns participants to either an experimental or a control group based on their last names, systematic differences between groups are created before the experiment even begins. This is a confounding variable referred to as _____

Answer 1

Answer: Selection bias

Explanation:

Selection bias is defined as the process in which individual or group of individual are analyzed for selection process by lacking randomization property .This process displays that selected sample of individuals is not similar representative of major interest population.

According to the question,the systematic difference that occurs in selected group for experiment as per their last name is  displaying that selected group does not represent interest population that is causing systematic error.Thus, this situation describes about selection biasing.