PPK vs CPK
PPK and CPK are mainly process capability indices. When PPK stands for Process Performance Index, CPK stands for Process Capability Index. Both PPK and CPK have very wide impacts on the performance strategy of organisations and they are very closely watched.
CPK or Process Capability Index is an index that measures how a process is running to its specification limits in relation to the natural variability of the process. CPK is a measure that tells how close an organisation is in achieving the target and how much consistent an organisation is with regard to average performance. On the other hand, PPK or Process Performance Index helps in verifying if the sample generated is capable to meet Customer CTQs.
When CPK is for only short term, PPK is used for long term. When the Process Capability Index shows how a process will do in the future, the Process Performance Index shows how a process performed in the past. It can also be seen that the process will be in a state of control in CPK where as it is not like that in PPK.
Unlike the CPK, PPK cannot be used to predict the future as the process in PPK is not in a state of control.
Process Capability Index is calculated by taking an estimate of the standard deviation. R-bar/d2 is the formula used for calculating CPK. On the other hand, Process Performance Index is calculated by using the normal form of standard deviation. Root of variance or square root of sum of squares divided by n-1 in the standard formula used for calculating PPK.
Summary
1. When PPK stands for Process Performance Index, CPK stands for Process Capability Index.
2. CPK is a measure that tells how close an organisation is in achieving the target and how much consistent an organisation is with regard to average performance. PPK helps in verifying if the sample generated is capable to meet Customer CTQs.
3. When the Process Capability Index shows how a process will do in the future, the Process Performance Index shows how a process performed in the past.
1. The process will be in a state of control in CPK where as it is not like that in PPK.
2. Unlike the CPK, PPK cannot be used to predict the future.
3. When CPK is for only short term, PPK is used for long term.