Parametric estimating is one of the tools and technique of processes like Activity Duration Estimating,Cost Estimating, Cost Budgeting.
Parametric estimating is a quantitatively based estimating method that multiplies the quantity of work by the rate.
This estimate is by multiplying a known element—like the quantity of materials needed—by the time it takes to install or complete one unit of materials. The result is a total estimate for the activity. In this case, 10 servers multiplied by 16 hours per server gives you a 160-hour total duration estimate.
The resulted estimattion is a total estimate for the activity.
-Posted by Sundar
Refer Exam Tips 3 – Key terms for PMP Exam for more key terms
Posted by Sundar 
Singapore Project Manager Forum 