Balanced designs for comparing test products with two controls in sensory trials

Sensory trials are an integral part of food and nutrition experiments involving agricultural/animal produce to demonstrate some sensory fact. To draw definite conclusion from the study, it is important to eliminate or minimize all sources of error, and recognize and control all factors that may influence or interfere with the result. In addition to various potential sources associated with the preparation of the test products, there may be variability due to measurement or assessment process, order effects, carryover effects, assessor fatigue etc. Sometimes, designs are required which can provide higher precision estimates for the crucial product comparisons, at the cost of the comparisons which are of lesser interest, and will be estimated with lower precision. One situation where there is special interest in a subset of product contrasts arises when control products are included in the trial. A control product provides a calibration standard, which can serve as a basis for comparison of results across studies may be helpful to the panel. Here, a series of treatment vs. control designs for multi-session trials are obtained to deal with such situations.