In addition, the standardization process includes an evaluation of the quality of the test. These terms are probably familiar to you, although they are easily confused. The reliability of a test refers to how consistent or stable the test scores are. If you take an IQ test on Monday and your IQ is 112 but on Wednesday your IQ is 80, then that test is not reliable. In addition to being reliable, tests should also be valid.
Validity refers to whether a test measures what it claims to measure.
Reliability and validity are independent of each other. A test can be highly reliable but not necessarily valid. IQ tests and most standardized tests are highly reliable across short periods of time. If you give a group of people a test and then re-assess them a few weeks later, the correlation between the first and second test will be very high. These questions also relate to the reliability of the test.