THE ROLE OF CONSUMER STUDIES IN RESEARCH Also, skin treated with the cream alone could be examined to find out how much effect is due to the cream and how much is due to X. Where three or more different products are to be assessed, it is more satisfactory to use a Round Robin design than to compare each product with the same standard. In a Round Robin, every possible combination of the products in pairs is made and each pair is tested in a paired comparison test. For n products there are n(•-l).possible pairs. The advantages of a Round Robin design are the possibility of ranking all products and the possibility of using smaller panels. For instance, if a fairly average control product is tested against some test products which are much "better" and some which are much "worse", comparison of each test product with the control product will classify the test products as better or worse. However, it will be difficult to assess exactly the degree of difference in each comparison and it will probably not be possible to place the products in any rank order. Round Robin testing compares each product with every other product and does allow all products to be placed in a rank order. Also, in order to get a significant answer for each comparison of a test product with the control product, fairly large panels will be needed. In a Round Robin design, however, information about a product can be obtained from every comparison in which it appears. Therefore smaller panels can be used for testing each pair. This will be considered further under Analysis of results. Factorial designs are useful when variations within a given formula are being considered. In practice the test is a Round Robin but the analysis takes account of the factorial design. There are occasions when it is not reasonable to ask panelists to test more than one product. This occurs when the product has a long lasting effect and the product would not be used again for a few weeks or when the product has to be used for a period of time to show any effect. Then Monadic testing must be used. When more than one product is under consideration, balanced panels must be drawn up, one to test each product. This means that each person in one panel must be matched by someone with similar charac- teristics in every other panel. The disadvantage of Monadic testing is the lack of a reference standard for the panelists. If products are compared with panelists' "usual brand" this could be any one of a number of different brands. Also, since the "usual brand" has a brand image, advertising claim, professionally designed pack

44 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS and presentation, the test product is at a disadvantage in such a comparison. By including a leading marketed product in the test some indication of relative merits can be obtained and the test will show up any major ad- vantages or disadvantages of the test products. The possible answer from a test should be considered at this stage to check that some use can be made of the results in fulfilling the objects of the test. QUESTIONNAIRES Obviously questionnaires are a very important part of consumer testing since one only gets answers to the questions one asks. All questions are loaded because they ask people to think and to put their thoughts into words. Normally we do not analyse in any detail our reasons for preferring one product to another. The art in drawing up questions is to devise those which do not make one answer more appealing to the panelist than another, which are clearly understood by all panelists and which give panelists the opportunity to express their feelings adequately. Three types of question can be asked: two way questions, multiple choice questions and free answer questions. Two-way questions are ones having a yes... no .... type of answer. e.g. "During the test did you use any other hair product?" Yes ..... No ..... This sort of question is the easiest to analyse but unless the issue is really clear cut into the two possible answers, it can be hard to answer without qualification. If panelists are asked which of two products they prefer, some of them will not have any preference, and this should be allowed for. Multiple choice questions give a pre-selected choice of answers and panelists have to select one of them. They can be very useful when all the possible answers are known in advance. They also serve to give an indication of the degree of feeling as well as the direction, if used as follows:- "Please indicate your rating of the product by ticking one of the following:- I liked it very much ...... I liked it moderately ...... I liked it slightly ...... I neither liked nor disliked it ..... I disliked it slightly ...... I disliked it moderately ...... I disliked it very much ...... "