The most serious disadvantage is the limited types of knowledge that can be assessed by multiple choice tests. Multiple choice tests are best adapted for testing well-defined or lower-order skills. Problem-solving and higher-order reasoning skills are better assessed through short-answer and essay tests.[citation needed] However, multiple choice tests are often chosen, not because of the type of knowledge being assessed, but because they are more affordable for testing a large number of students. This is especially true in the United States where multiple choice tests are the preferred form of high-stakes testing.[