A fat-finger is a manual keying mistake: 1.52 typed as 15.2, a value entered under the wrong lot, two digits transposed. On a control chart it looks like a dramatic flyer and can trigger an OCAP, a tool-down or a scrapped lot if nobody checks the raw data first. Automated data collection removes most of them, which is why manual entry fields on SPC systems often carry range checks.
That 2.9 micron point is a fat-finger, the traveler says 0.29. Correct it in the system and annotate the chart.
Also heard as
- fat-fingered entry
- keying error
- typo
Related terms
Flyer
Single wild data point far from the rest, often a measurement or entry error rather than a real process change.
OCAP
Out-of-control action plan: the scripted checklist that tells operators exactly what to do when an SPC chart fires.
Outlier
Observation that sits far from the pattern of the rest of the data, either a genuine extreme or an error.
OOC
Out of control: shorthand for a point or chart that has violated a control limit or run rule.