The By Operator graph shows all of the measurements taken in the study, arranged by operator. The measurements are represented by dots; the means by the circle-cross symbol. The line connects the average measurements for each operator.

Ideally,

·    the measurements for each operator will vary an equal amount

·    the part averages will vary as little as possible

The temperature data meets both of the ideal criteria above. There will always be some variation, but it appears the operators are measuring consistently.