Correction is the action taken to rectify the error. Corrective action is what is taken to rectify the cause of the error. Preventive action, on the other hand, is the action taken to prevent the cause by looking at the problem holistically.
Correction: In an academic setting, a student score recorded wrongly by an academic assistant warrants correction
Corrective Action: Time is to be invested in a Corrective action if all possibilities of an error or a non-conformity being a one-time instance have been eliminated. For instance, if it has been confirmed that there are possibilities for erroneous entries in the future one may seek the answer to the question "What can be done to ensure that scores are recorded correctly?". 2-level checks into the entry before the results are declared by the Examination cell is a corrective action. An automated system that validates the numbers that are entered or pops up a check question about the entry are all corrective actions.
Preventive action: Consider the following question
"Why was there an error in the score entry by the assistant ?".
Was there a lack of proper instructions given?
Was the time crunch during the time of data entry?
Were there too many interruptions while the data entry was happening?
Was the Academic Assistant multi-tasking during the time of data entry?
Is the work condition conducive for the job given?
Are there consequences for making such errors - Penalizing the operator/ Incentives for error-free data entry?
Creating an environment that facilitates/encourages error-free data entry is preventive action
In situations which are one of a kind - Special Cause: For example, in the academic setting a student who may have missed the exam due to illness is a non-conformity towards 100% attendance but is beyond the control of the process. Preventive and Corrective actions may not help in here..... A re-exam is the correction that can be put in place.