1. Validity refers to the degree to which a tool measures what it is intended to measure. There are several types of validity including content validity, criterion-related validity, and construct validity. 2. Reliability refers to the accuracy and consistency of a measuring tool. A reliable measure produces nearly the same results during repeated measurements. 3. Sensitivity refers to a measure's ability to detect changes, while appropriateness means a measure evaluates what it is intended to without bias. Objectivity, economy, practicability, and interest are also important factors when selecting a measurement tool.