Face validity is the simplest and least scientific definition of validity. Face validity concerns the superficial appearance, or face value, of a measurement procedure. Does the measurement technique look like it measures the variable that it claims to measure? For example, an IQ test ought to include questions that require logic, reasoning, background knowledge, and good memory. Such questions appear to be appropriate for measuring intelligence and, therefore, have high face validity. Face validity is based on subjective judgment and is difficult to quantify. In addition, there are circumstances in which a high level of face validity can create in a research study can see exactly what is being measured and may adjust their answers to produce a better self-image. For this reason, researchers often try to disguise the true purpose of measurement devices such as questionnaires, deliberately trying to create a measurement technique that has very little face validity.