In statistical process control $($SPC$),$ special or assignable causes of variation

can be present in a process that is fully capable of meeting specifications consistently

are used to determine the upper $($UCL$)$ and lower $($LCL$)$ control limits on a control chart

are of secondary importance in quality control procedures used to detect and eliminate variation

are outside, nonrandom problems such as breakdown of machinery, material variation, or human error

$$ are intrinsic to the process and will always be there unless the process is changed