Which type of error does not affect the reliability of an instrument?

The type of error that does not affect the reliability of an instrument is unsystematic error. Reliability refers to the consistency of a measurement, or the degree to which an instrument produces stable and consistent results across repeated trials. Unsystematic errors, also known as random errors, occur in an unpredictable manner and can vary from one measurement to the next. While these errors may introduce some variability in the data, they do not bias the results in a consistent direction and, therefore, do not impair the reliability of the instrument.

In contrast, systematic errors consistently skew the results in one direction, leading to a bias that affects the accuracy and reliability of the measurement. Measurement errors encompass both systematic and unsystematic errors, and as such, they can impact reliability selectively or collectively, depending on their nature. Human error typically involves mistakes made by the individual administering the instrument or interpreting the results, which can also impact reliability. Understanding this distinction is vital for proper assessment and evaluation in appraisal practice.