The selection of small samples at regular intervals of time, where the sampling units within a sample were produced as nearly as possible at the same time and under the same conditions - method of rational subgroups . We use statistics to gain insight into the management of business processes. A pattern of reasoning that allows us to understand, then improve, processes through studying the variation in the data. Recall that a process is a set of conditions that repeatedly come together to transform inputs into outcomes. Suppliers provide the inputs .
Outcomes go to the customers of the process.
A statistical variable used to characterize the quality of process outcomes. Represent numerical quantities of a concept of interest. Names or classifications are used to divide data into separate groups. Measurements that rank observations into categories following a natural ordering. Numerical measurements in which zero is a meaningful value and the difference between values is important.