The assessor is then presented with the next set of three sample choices, one of which contains the diluted odor sample. However, this next set of three samples presents the odor at a higher concentration (i.e. two times higher). The assessor continues to additional higher levels of sample presentation following the “triangular forced-choice” procedure and the required designation of “guess”, “detection”, and “recognition”. This statistical approach of increasing levels of sample presentation is called “ascending concentration series.”