The test items are divided into halves, with the items of the two halves matched on content and difficulty. The halves are then scored independently and the results compared. One of two formulas is used depending upon the difficulty level of the items. For published test and inventories, the reliability coefficient and method used should be contained in the manuals. Longer tests and instruments are generally more reliable.
Achievement tests are more reliable that attitude inventories.
Validity relates to the appropriateness of the interpretation of the results. Does the construct explain or relate to behavior. Reliability is not a sufficient condition for validity. Validity does imply reliability. Quantitative Data Preparation Preparations must be made to ensure that the data is scored and recorded in a usable format.