The Concept of Utility-

The concept of utility has been developed as a common scale for evaluation of a product on a number of diverse dimensions such as cost, safety and ease-of-use. This scale is based on the personal preferences of the evaluator, and as such, is highly subjective. The utility of a product on a particular quality dimension measures the usefulness of that particular quality characteristics of the product in the opinion of the evaluator. Thus, the utility of a design on, say, the adaptability dimension is a measure of the contribution of the adaptability of the design to the overall usefulness of the product. The overall utility of a product is the sum of utilities of each of the quality dimensions

Specifications-

Writing specifications usually calls for collecting information. The designer also needs to collect information about how high a person can write and how he can comfortably reach. This information would again be stastical in nature and the designer has to make a decision as regards how tall a person he should design the lowest point on the board for, and how short a person he should highest point on the board cater.