Unavoidable (“Nuisance”) Factors

In the context of many factors acting together, some uninten­tional, often unperceived or unavoidable, factors that cannot be accounted for may influence, to an unknown extent, the quality characteristic. For example, vibrations in the building, noise, illu­mination, room temperature, humidity, and so forth, can have an effect when the experiment involves only inanimate objects. When animals are involved, more “biological” factors appear, and when humans are involved, more “human” factors are added to the list. Collectively, these are known as nuisance or noise factors. There are three aspects to the existence of such factors:

1. Their influence on the quality characteristic or summary effect, acting alone or with other factors, may be ignorable or considerable in extent.
2. The experimenter’s awareness of these factors may vary from vague suspicion to real concern.
3. When there is concern, the experimenter’s ability to compensate for them may vary from total help­lessness to complete control.

Confined to the “triangle” of these three sides, figuratively speaking, nuisance factors have sway in most experimental research. Fortunately, some control is possible, whether noticed or not, by the experimenter, by means of randomization, which is dealt with in Chapter 16.

Source: Srinagesh K (2005), The Principles of Experimental Research, Butterworth-Heinemann; 1st edition.