What is the term for an observer's distortion of measurement, whether intentional or not?

The term that describes an observer's distortion of measurement, whether intentional or not, is observer bias. This bias occurs when the observer's expectations, beliefs, or personal influences affect the outcomes of their observations. It can happen consciously or unconsciously, leading the observer to misinterpret data or influence results based on their perspective. This concept is particularly important in research settings where objective data collection is critical, as it can significantly affect the validity and reliability of the findings.

The other terms refer to similar but distinct concepts. Systematic error refers to consistent inaccuracies in measurements, typically resulting from flaws in the measurement system or methodology, leading to results that deviate from the true value in a predictable way. Random error, on the other hand, pertains to unpredictable variations in data that arise from random factors and do not consistently skew results in one direction. Instrument bias specifically relates to inaccuracies inherent to the measuring tools themselves, which can lead to distorted data but does not encompass the broader spectrum of observer influences.

In summary, while other terms address various aspects of measurement inaccuracies, observer bias specifically highlights the role of the observer's perception and judgment in distorting measurements.