When a normal curve is graphed it appears as a bell shaped curve. The results of a tested student can then be placed on the bell curve indicating a score. This score can then be used to compare a student or groups of students to a larger group of students, local, state or national. Test publishing companies usually normalize their tests every 5-7 years. Standardized tests should be reliable and valid.
Reliability refers to the test construction.
Reliable tests should be dependable to report similar results when taken by similar groups over a period of time. In other words, the test is free from errors in its construction and measurement. Therefore, if a test is reliable, it should be meaningful. Validity refers to the test taking. The test is actually measuring what students are learning.