The Career Key test measures the strength of six Holland personality types. These types are based on Holland career choice theory, the one most widely used by professional counselors - and the subject of hundreds of scientific studies. The Career Key test can be taken using paper-pencil or online. Validity and reliability studies have been run on this instrument.
CareerKey.org provides a link to purchasing the Career Key instrument (both paper-pencil and online versions) in multiple languages as well as various other resources produced by Career Key.