Quality is not a property in itself. It can be stated that quality is always related to costs. This is the reason why one could speak about the quality-cost-complex. Both factors are interrelated. Better research designs or bigger samples or both cost more money. When designing a piece of market research one should always look for an optimum between costs on one side and quality on the other side. The problem can be formulated in the following form: How do we reach an optimum between research costs at one side and research yield, also in terms of quality, on the other side. Or in terms of the optimum: How do we reach optimal results, c.q. quality for a given amount of money or given the degree of accuracy of the answers and a certain standard of quality at as less an outlay of money as possible. When defined in such a way the term quality, which is vaque in itself, is given an economic content. An optimum is not a minimum. Quite often quality can be substantially improved by spending some more money.