[求助]这辆个假设该怎样理解

This method(Gage R&R study -crossed) is suitable for non-destructive testing. It can also be used for destructive tests when the following assumptions have been met:

·All parts within a single batch are similar enough to claim they are the same part

·All operators measure from each batch

请教各位该怎样理解这两个假设，谢谢(?