Standardized Tests are those tests with carefully designed procedure, questions and administration. Often achievement tests, the tests measure the performance of large numbers of individuals to collect information about individual children or adults, or to assess the success of school wide educational programs.
First, the Questions are standardized. A testing organization spends a lot of time and effort on individual items to be sure that the particular items are not poorly written or confusing. They try them out with many groups of children before they make the items part of the test.
Secondly, the Procedures are standardized. When the test is designed, the directions for each section are carefully written and the person administrating the test will read the directions exactly as they are read in other places at other time. The time for each test section is pre-determined. A child taking the test will gave exactly the same amount of time for each section as a child taking the same test on the other side of the globe or the other side of the country.
Finally, the Administration is standardized. This may be redundant, because we are talking about procedure. Still, one of the essential parts of standardized tests is the understanding that it is administered exactly the same way each time it is given.