What is an Experimental Section?
On both exams, the experimental section is a section of the test that does not count toward a student’s score. It enables the test administrators (The College Board for the SAT, and ACT, Inc. for the ACT) to collect data about new test questions in a controlled environment. This is nothing new: the SAT and ACT have included an experimental section for many years. Prior to the 2016 redesign of the SAT, it was one of the nine multiple choice sections of the test, and was usually difficult for students to detect while they were taking the exam. For the ACT, it has always been an uncounted fifth and final section of the test; until recently, it was given only to those students who opted not to take the writing (essay) portion of the ACT. After the 2016 SAT redesign, the College Board followed suit, administering an experimental section as the final section of the test for students not taking the essay.
Structure and Changes
For both exams, the experimental section is twenty minutes long, and can feature questions from one of any of the other four graded sections. Students familiar with the structure of the exams will know it's experimental, and could choose to select random answers—or no answers at all—secure in the knowledge that doing so won't affect their scores. Despite the potential for test takers' flippancy, it still makes sense for the College Board and ACT to administer the experimental sections: there will be enough students who will treat them as if they'll count, and who will thus provide valuable data to the test creators.
Because it used to be the final section of only the tests that did not include the optional essay, the experimental section was a minor annoyance for a subset of students, and didn’t detract from any sections that counted. In the fall of 2018, however, both the SAT and ACT began including the experimental sections for all students taking the tests under standard timing conditions—even those sitting for the essay. (Students with extra time accommodations are exempt.) For students taking the essay, the experimental section comes immediately beforehand.
All students who take the SAT or ACT under standard timing conditions will be required to test for an additional twenty minutes—a non-trivial addition to an already 4-hour exam. It is important that students are aware that they will encounter the experiment section, but that it will not count toward their scores. Though students won't be happy sitting for the extra time, students should take comfort in the fact that this extra "surprise" section won't factor into their test results.