The causes of variation in statistical process control are

natural causes and assignable causes.

Explanation:

Common cause variation.

Explanation:

this is intrinsic to the process and will always be present Special cause variation, which stems from external sources and indicates that the process is out of statistical control Various tests can help determine when an out-of-control event has occurred.

1) d

2)c

3)b

4) a

5)c

6) c