Example of a Covering Array with No Factor Level Restrictions

The data in this example pertain to interoperability in the area of software testing. There are four factors of interest:

• Web Browser (Safari, IE, Firefox, Chrome, Other)

• Operating System (Windows or Macintosh)

• RAM (4, 8, or 16 MB)

• Connection Speed at three settings (0-1, 1-5, or greater than 5 Mbps)

You are interested in finding out which combinations of these factors are likely to cause failures.

The response is whether the system functions properly for each combination of factor settings.

Testing each combination of settings would require 90 (5x2x3x3) trials. To keep the run size manageable, you decide to require Strength 3 coverage, indicating that all combinations of any three factors are tested.