Today, we will explore the questionnaire method in psychology, a widely used tool for collecting data on various psychological constructs. This method allows researchers to gather information efficiently from large samples, making it essential in both academic and applied research. A questionnaire is a research instrument comprising a series of questions designed to gather information from respondents, administered in-person, by mail, over the phone, or online. It has historical roots in the early 20th century with significant contributions from social scientists like Charles Booth and Karl Pearson. Notable examples of questionnaire use in psychology include the Minnesota Multiphasic Personality Inventory (MMPI), Beck Depression Inventory (BDI), and Rosenberg Self-Esteem Scale. Understanding the strengths and limitations of this method is crucial for effectively designing and administering questionnaires in psychological research.