Before you decide to embark on experimental research you need to be very sure about what you are doing and the level of control you have over the situation. An experiment is a controlled research situation, which means ‘(a) that unwanted variables and external influences can be kept out of the experimental environment, and (b) that the researcher can establish the experimental conditions down to the smallest details’ (Corbetta, 2003, 94). When these conditions are not entirely met then the researcher has a responsibility to identify the extent of the error. ‘Experimental error occurs when a change in the dependent variable’ (Burns, 2000, 134). As we can have no way of controlling all variables acting on a human subject at any one time, not only can we never avoid experimental error but the majority of the time we cannot locate the variable responsible for the error, therefore we are unable to measure the extent of error. A true experiment eliminates the effects of all intervening, spurious and antecedent variables. Tests and trails are not experiments and should not be labeled as such in a research context. If you intend to carry out an experiment, then you must understand the nature of experimentation and experimental error to enable you to establish the level of significance of any inferences drawn from your research.