① Quality Improvement

A stable process can have "trends" within the range of its normal variation. Use the rules for randomization to ensure signs of an "unstable" system, giving support to the hypothesis that the changes resulted from your actions, before proceeding with the analysis of whether your improvement is "legitimate" (effective).

A legitimate QIP is a process that achieves a benchmark rate of continuous improvement. The hypothesis is that any defect level, subjected to legitimate QIP, decreases at a constant rate, so that when plotted on semi-log paper against time, it falls on a straight line, making it easy to extrapolate.

② Control Charts

Statistical process control (SPC) charts are chronological graphs of process data that are used to help understand, control, and improve processes. Although based in statistical theory, SPC charts are easy to interpret for hospital personnel. This section deals with the types of control charts in common use, simple methods for determining appropriate sample sizes, and methods for dealing with rare events and low occurrence rates.

SPC is well-established in other industries and has a long history of use for measuring process performance and improving outcome quality. In healthcare, important applications include their help to reduce rates of adverse drug events, surgical site infections, patient falls, central line infections, surgical complications, and many other types of iatrogenic injury and adverse events.