This document discusses research design. It begins by defining research design as the arrangement of conditions for collecting and analyzing data to combine relevance to the research purpose with economical procedures. The document then outlines the key parts of research design including sampling, observational, statistical, and operational design. It also discusses important concepts such as independent and dependent variables, extraneous variables, hypotheses, experimental and control groups, and treatments. The document concludes by describing three main types of research design: exploratory, descriptive/diagnostic, and hypothesis-testing designs. It provides examples of methods used for each type of design.