A flyer is one isolated reading that lands well away from its neighbors and is not followed by a shift or trend. Before treating it as a special cause, insiders check the gauge, the sample, the recipe and the data entry, because many flyers turn out to be measurement artifacts. Confirmed flyers are annotated on the chart and usually left out when limits are recalculated.
One flyer at 312 nm on a 250 nm target, remeasure read 251. Bad CD-SEM read, not the wafer.
Also heard as
- freak
- wild point
- flier
Do not mix it up with
- Outlier: Outlier is the formal term for any point inconsistent with the rest of a data set; flyer is the shop word for a single wild point on a time-ordered chart.
Related terms
Outlier
Observation that sits far from the pattern of the rest of the data, either a genuine extreme or an error.
Fat-finger
Data entry error from a mistyped number, such as a slipped decimal or swapped digits, that shows up as a false signal.
OOC
Out of control: shorthand for a point or chart that has violated a control limit or run rule.
Special cause
Specific, identifiable source of variation that is not part of the process's normal behavior and shows up as a chart signal.