1. Validity: The extent to which a test measures what it is supposed to measure.
The truthfulness or accuracy within the score of a test or interpretation of an experiment.
How should a reading or listening test be designed?
What does the TOEFL evaluate?
2. Reliability (consistency) : The extent to which individual differences are measured consistently.
Does a clasroom, its conditions or the environment affect students` results? E.g: a marching band… health or personal problems:a fever. Taking the listening part at a noisy place? With poor equipement?