The document discusses key elements of research design including the purpose of studies, types of investigations, study settings, populations, time horizons, and units of analysis. It also covers measurement scales, reliability, and validity. The purpose can be exploratory, descriptive, or for hypothesis testing. Studies can be causal, correlational, contrived or non-contrived. Populations can be individuals, groups, organizations or cultures. Studies can also be cross-sectional or longitudinal. Proper research design ensures the purpose is effectively addressed.