Using Control Charts to predict number of potential customers - Part Two

In this control chart, managers are looking at the number of visitors to the show sites who have shown “more than a passing interest” in buying. This is subject to a good counting process with workable operational definitions, of course.

But comparing this chart with the previous Total visitors chart is interesting. The apparent winter/summer split is replicated, as is the special cause signal at Easter, but not so at August Bank Holiday. The summer system is more or less stable, with an average of 56 qualified prospects, varying predictably between 28 and 85.

So only around 1 in 4 of all visitors to show sites look like real potential customers. So is management trying to increase the total number of visitors to site? Or trying to improve the conversion process from what is known in the trade as a “carpet-treader” to genuinely interested prospects? It depends on their knowledge of the local situation, of course, but these are important questions that show that management is looking at the System, and not wasting their energy on the week-to-week vagaries of natural variation.

As a twist to the tale, management had a theory that increased spending on advertising at holiday time merely increased the total number of visitors to site, without a commensurate increase in nett visitors. So the following year, and with not a little trepidation, they did not spend additional money on holiday-time advertising. The result was as expected. The nett visitor numbers behaved exactly as they would have done with the advertising, and the Regional manager had saved £100,000 on the advertising budget which could be spent on other marketing experiments.