Accounting software support data
Use the Left and Right buttons to show that sometimes there seem to be two clusters but at other times the gap in the middle disappears.
The dependence of histogram shape on the choice of classes means that it is better to use a stacked dot plot for small data sets.
An software company offers free technical support for one product (an expensive accounting package) via email. In order to monitor the ongoing costs of this service, the company records the time taken to deal with each emailed query. The table below shows the number of minutes taken to answer all of the 20 queries in one week.
Without further supporting evidence, the clusters are not pronounced enough for us to conclude that the batches of iron ore must form into two meaningful groups. However they do give an indication of clustering that a good 'data detective' would investigate further.
(Further investigation showed that the clusters did correspond largely to two different types of query — from new users and from experienced users.)