Please note that this advice is only a rough guide to the methods that are appropriate to your investigation. Only the simpler experimental designs are dealt with here. If you require a fuller appreciation of the statistical methods for your investigation then you are strongly advised to consult a reputable text and/or a statistician. A common fault is to read an article which is related to your work and repeat the methods that have been used by the authors; do not assume that all journals weed out bad statistical methods.