Control attempt
A control experiment (also trial control , control experiment ) is in the exact sciences an accompanying experiment to exclude disruptive factors or to verify the methodology developed for an experiment . Control experiments are a central part of the scientific methodology . Ideally, there are controls for every possible variable in an experiment .
properties
Control tests are based on the ceteris paribus principle and can either rule out individual causes for a result ( negative controls ) or demonstrate the functionality of the method in principle ( positive controls ). A group assigned to a control experiment is called a control group.
Positive controls are accompanying experiments in which a phenomenon (or an effect ) achieved with the main experiment will certainly occur. Positive controls are used to demonstrate that a method works with the known values of the variables ( method validation ) and can therefore rule out false negative results from an experiment.
Negative controls are accompanying experiments in which a phenomenon (or effect) achieved with the main experiment does not occur ( zero value ) or should not occur. This ensures that a positive finding in the main experiment can only have been due to the change in the variables. A positive result of the negative control, on the other hand, indicates a lack of specificity of the respective main experiment, ie the effect achieved in the main experiment also occurs due to other influences. Negative controls serve to exclude reasons ( sources of error ) other than the hypothesis for a phenomenon and serve to avoid incorrect interpretations of false positive results. This reduces the possibility of falsifying the hypothesis after it has been published . If the results of the experiment and the negative controls are negative, it can be concluded that the outcome of the experiment is independent of the variables; H. the change in the variables had no effect on the outcome of the experiment. In animal experiments, placebo administration is a typical negative control. Additional negative controls to examine the influence of the subject's level of knowledge, and in the latter case also of the experimenter, on a test result are avoided by means of blind tests and double- blind tests . Strategies for the division of test groups in clinical studies are e.g. B. the randomization and the parallelization .
example
When residents of a village about electrosmog complain, one can fake a transmitting antenna be placed as a negative control. Radio signals cannot emanate from the dummy. If the residents complain about the new effects of electrosmog, this result is false positive and must have another cause.
literature
- Douglas C. Montgomery: Design and Analysis of Experiments. 8th edition, Wiley, 2012, ISBN 978-1118146927 .
- Graeme Ruxton, Nick Colegrave: Experimental Design for the Life Sciences. 3rd edition, Oxford University, 2010, ISBN 978-0199569120 .
Individual evidence
- ↑ Johnson PD, Besselsen DG: Practical aspects of experimental design in animal research Archived from the original on May 29, 2010. Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. In: ILAR J . 43, No. 4, 2002, pp. 202-6. PMID 12391395 . Retrieved June 24, 2013.
