I run a query and use the avg to return a value of 18 and use StDev and get a value of 36. Does this mean that 36 is the maximum value of the standard deviation or am I suppose to divide that by two to get my range on either side of the 18? Does anyone know what that value is?

Use a search engine to look up 'Standard Deviation Definition'

One link returned is" http://www-fp.mcs.anl.gov/otc/Guide/CaseStudies/port/variance.html