http://www.1biz-dir.com/business_and_economy/Appraisal_and_Estimators/One business web directory orientated for best website optimization and recognition which gives unlimited online access to the most accurate, up-to-date company profiles for ALL businesses in the U.S. and Canada and threwout the world. Add your business.. In statistics, an estimator is a function of the observable sample data that is used to estimate an unknown population parameter; an estimate is the result from the actual application of the function to a particular set of data. Many different estimators are possible for any given parameter. Some criterion is used to choose between the estimators, although it is often the case that a criterion cannot be used to clearly pick one estimator over another.