StatsComponent - get min, max, sum, qt, avg of number fields

StatsComponent - it returns min,max,sum,qt,avg of specified number fields:

request parameters:
&stats=on&stats.field=price

<stats>
 <stats_fields>
   <lst name="price">
       <double name="min">10</double>
       <double name="max">30</double>
       <double name="avg">20</double>
       <double name="sum">60</double>
       <double name="qt">3</double>
   </lst>
 </stats_fields>
</stats>

WRT "stats", the component can output sum and avg, but not sd and var.

USE CASE:
StatsComponent can be used to get "market price" of DocSet e.g. rental housing site, package tour site.