High Quality Content by WIKIPEDIA articles! Statistical models of the sources of data and typical problem formulation: 1. Sampling from a finite population 2. Measuring observational error and refining procedures 3. Studying statistical relations Generating informative data using optimization and randomization while measuring and controlling observational error. Optimization reduces the cost of data while meeting statistical needs, while randomization warrants reliable inferences: 1. Design of experiments to determine treatment effects. 2. Survey sampling to describe natural populations