Priority vs Severity vs Impact

I have come across multiple project managers and teams managing Level 2 and Level 3 IT support projects who struggle to articulate the EXACT definitions of Priority, Severity and Impact. Also these 3 terms (especially Priority and Severity) are used interchangeably by project teams. Here is my small attempt to explain the same with some examples.

Impact is the way in which an Incident affects the core business or revenue of the organization. A high impact defect has the potential to stop core business operations or even cause revenue losses. Typically Impact of the Incident does not change with time. Below you can see sample definition of various levels of impact. These can be changed or modified as per the business you or your team is supporting.

1-High: Defects resulting in failure of key Organization business processes impacting revenue. There is no work around available.

2-Medium: Defects impacting business processes. Key components are down and major functions are not working. No immediate / serious impact but has potential to affect revenues. Unreasonable work around exists.

3-Low: Defects impacting functions that have a low/negligible impact on key business process. Reasonable workaround exists.

Urgency suggests the amount of delay acceptable in resolving a particular incident and is always associated with time. A high urgency incident will have minimal acceptable delay in resolution. The Urgency of the Incident can increase as the age of the Incident increases.

1-High: Very urgent incident which should be treated as quickly as possible

2-Medium: Urgent incident which should be treated quickly

3-Low: Incident that is not urgent and resolution can wait for some time

Priority is defined as a combination of Impact and Urgency (Priority=Impact X Urgency) and is defined as per the below table

	Impact
Urgency		1-High	2-Medium	3-Low
	1-High	P1	P2	P3
	2-Medium	P2	P3	P4
	3-Low	P3	P4	P5

Below example will help you to understand the above definitions better 

Example: Incident logged that a particular feature has to be added on www.phutwa.com site effective 31-Dec which will increase user hit rate on website. For this to happen QA team need to provide sign off on this feature in lower environment by 01-Dec. Development team started working on the feature, but while testing it in lower environments team found it had some defects.

• 01-Nov: On 01-Nov, the defect will have Impact: Medium, Urgency: Low
• 20-Nov: If still unresolved, Impact:Medium, Urgency will change to  Medium
• 30-Nov: If still unresolved, Impact:Medium, Urgency will change to High

In the above example Urgency of the defect remains same but its Urgency keeps on increases as we reach near to a critical date of 01-Dec.

Hope the above definitions and examples will clarify the differences and relations between all 3 terms. Please feel free to comment with your views.

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