The Riso-Hudson Enneagram Type Indicator (RHETI, Version 2.5) is an 18-page paperback booklet Offprint of the personality questionnaire available in their best selling book, DISCOVERING YOUR PERSONALITY TYPE (Houghton Mifflin, 1995). The RHETI consists of 144 pairs of statements in a forced-choice format; it is self-scoring and takes approximately 40 minutes to take and score.
The RHETI has sold over 100,000 copies in book form, and is consistently in the top 15 Enneagram books on Amazon.com. The Offprint has sold 27,000 copies in Version 2.0 from The Enneagram Office, and an additional 39,000 copies in Version 2.5 for a total of 66,000 copies from our office.
The RHETI is the acknowledged "gold standard" in Enneagram based personality tests, and is widely available in foreign translations (Japanese, German, Dutch, Norwegian, and French, and Spanish among them) and used in a variety of self-help, therapeutic, and business and organizational settings.
It is approximately 85% accurate for determining basic type; when the top three scores are considered, the RHETI is even more accurate since the person's real type is almost certainly one of them. Academic validation of the RHETI is underway at the University of Akron, as well as by graudate students in the United Statesand Hong Kong. [via]