"Garbage in, garbage out." Abbreviated as "GIGO", this methodological maxim, cranked out by first-generation computer specialists back in the 1960s, is anything but rubbish, even though it obviously does not apply to recycled garbage, trash or rubbish processed into usable stuff or energy. Coined to describe and predict the correlations between low-quality computer-data input and low-quality data output, it also applies to questions and questionnaires-including employment and employee-related forms of these.
Applied to the personnel assessment and survey fields, the GIGO mantra validly sums up what happens when a flawed question or psychometric inventory "item" (discussed below) as input is posed to elicit an output response, whether in a very sophisticated psychometric expert designed questionnaire, test, ratings scheme, "inventory", survey or one written for an upcoming interview by an HR manager on a lunch break and on a napkin.
The more useless or problematic the question, the more useless or problematic the answer. On analogy with "Ask me no questions, I'll tell you no lies", it translates into "Ask me no problematic questions, I'll hand you no problematic or blank answers."
Irrespective of whether the question is a stand-alone interview question or an item in a formal, scientifically-crafted extensive questionnaire or survey, the GIGO principle holds, although with some caveats or exceptions.