Standardized tests are more rigorous and scientifically developed than teacher-made tests. They require a panel of experts including content specialists, test designers, and teachers to plan the test, write items, test the items, and establish validity and reliability through field testing and statistical analysis. The process ensures the tests accurately measure what they aim to without bias. Teacher-made tests are simpler to create by individual teachers and better tied to local classroom needs, but are not as reliable or valid as standardized tests due to less rigorous development and analysis. Both have advantages for different assessment purposes.