When the 19th century economist Vilfredo Pareto observed that twenty percent of the population enjoyed eighty percent of the wealth, he never imagined that his observation would one day have the wide application it does today under a principle named after him. For example, it is said that twenty percent of most sales staffs do eighty percent of the volume. I disagree with that apportionment on two grounds. First, it fails to take into account that open and closed probes do not tend to elicit the same kind of information from the customer and, therefore, should not be weighed as apples to apples. Attempting to set up a mathematical ratio between open and closed probes would be much like attempting to balance eighty watermelons against twenty apples.
Open probes tend to raise the window of opportunity more significantly than do closed probes.
The reason lies in the different nature of the two probes. Because of this, it is unrealistic to direct salespeople to use four times as many open probes as closed probes. Such a directive would make of selling a mathematical situation which clearly it has never been nor ever will be. Selling is too protean to be held within the confines of some memorized mathematical formula. Proteus, you may remember was a Greek sea god who could change his form at will.