Distribution-free control chart

A distribution-free control chart is a type of chart which tracks changes to a process over time, without making any assumptions about what type of pattern the data follows. This is useful because it means that the chart can be used to track changes to the process without having to know what the data looks like. The chart usually plots values from the process on the horizontal axis, with the vertical axis showing how much the process has changed over time. The chart also usually has lines showing normal upper and lower limits for the process, so it is easy to spot when something abnormal is happening. If something abnormal is happening, it's important to investigate what the cause is.