Analysing treatment means in plant tissue culture research

Many researchers set up an experiment, make measurements, do an analysis of variance, calculate the mean response for each treatment, and then try to decide if the treatment means are significantly different and why. Much too frequently, Duncan's multiple range test is used to test differences among means. It is only one of a number of techniques that can be used to examine treatment means. Some researchers are unaware of the different techniques and that the interpretation of the results of an experiment is strongly influenced by the technique used i.e. using two different techniques might produce two different interpretations of the results. Selection of the appropriate technique to use for a particular experiment depends upon the nature of the treatments and the objectives of the research. This paper discusses four techniques (ranking treatment means, multiple comparison procedures, fitting response models, and using contrasts to make planned comparisons) that can be used to examine treatment means and presents examples of the use of each one for plant tissue culture research.Abbreviations (IAA) indole-3-acetic acid - (IBA) indole-3-butyric acid - (NAA) naphthalene-acetic acid - (2,4-D) 2, 4-dichlorophenoxyacetic acid - (BA) benzyladenine - (PBA) tetrahydropyranylbenzyladenine - (2iP) 2 isopentenyl adenine - (2iPA) 2 isopentenyl adenosineJournal Paper J-12661 of the Iowa Agriculture and Home Economics Experiment Station, Ames. Project 2210.