When tests are scored objectively vs. subjectively the reliability will be greater. The shorter the time interval between the administration of the test, the higher the reliability Variation with the testing situation. Errors in the testing situation can cause test scores to vary. The validity of a test is the extent to which the test measures what it says it measures. A test is valid if it measures what it intended to measure.
Reliability is a prerequisite of validity.
Reliability must be demonstrated before evidence of validity can be considered. This measures the extent to which the test items reflect the instructional objectives of a test. This is the most important type of validity for achievement tests. An estimate of the content validity of a test is obtained by thoroughly examining the test items to determine if they reflect the instructional objectives and the content that was intended to be tested. Content validity is usually evaluated by a group of specialists in tests and measurements who determine if the test content reflect the objectives.