When evaluating an instrument's validity, practitioners should be:

The concept of validity in evaluation refers to the extent to which an instrument measures what it is intended to measure. Practitioners looking at an instrument's validity must consider all available evidence regarding its effectiveness. Being "convinced by the preponderance of evidence" signifies that one should weigh multiple forms of data, research findings, and testimonials to draw an informed conclusion about the instrument's validity. This holistic approach allows practitioners to gather a more comprehensive understanding of the instrument's performance and fidelity of measurements across various contexts.

In contrast, focusing solely on construct validity would neglect other important aspects of validity, such as criterion-related validity or content validity, which are equally essential in ensuring that an instrument functions effectively. Not concerning oneself with historical data dismisses a valuable source of insights that can inform current evaluations. Lastly, being surprised by individual test results indicates a lack of preparedness, suggesting that practitioners are not adequately understanding the data or the instrument's established reliability, which undermines the essence of carefully evaluating an instrument's validity. Thus, gathering and evaluating the preponderance of evidence is crucial in ensuring proper assessment and interpretation of the validity of an instrument.