Data collection is a fundamental and critical part of descriptive statistics.
Good collection techniques are essential to comprehensive analysis and sound conclusions being obtained from data. This paper describes observational studies and controlled experiments, amplifying the brief discussion of these investigations in the text. In subsequent chapters of the text we will examine surveys and polls, where the behavior of a large population is determined by interviewing or polling a carefully selected small sample of the population. An observational study is an investigation in which data is collected by merely observing a situation or environment without actively intervening into the situation. An example is an investigation of the link between cigarette smoking and lung cancer.