An optical answer sheet is a form which is covered in a numbered and lettered grid of bubbles. These bubbles can be filled out by users to convey specific information, and the completed optical answer sheet can be fed through a machine which is capable of reading and interpreting the filled out bubbles. These sheets are used extensively in education, but they have other uses as well. Optical answer sheets are also called bubble sheets, in a reference to the bubbles which the user fills in, or Scantron® sheets, in a reference to a major optical scanning company.
In the educational field, an optical answer sheet is paired with a multiple choice examination. As the test-taker reaches a numbered question, he or she fills out the lettered bubble which appears to be the best answer. The teacher can feed an answer key into an optical scanning machine and follow the key with the completed bubble sheets. The machine marks any wrong answers on the bubble sheets and typically indicates how many questions were answered correctly on each sheet to make grading easy for the teacher.
Standardized testing relies heavily on the optical answer sheet to streamline the process for quick and accurate results. In some colleges and universities, students actually have to purchase their own optical answer sheets when they sit for examinations, although the sheets are generally provided free of charge to students in public elementary, middle, and high schools.
Optical answer sheets are also used for generic forms by government agencies and groups who handle large amounts of paperwork. People can fill out these sheets with information like their names, addresses, and so forth, using corresponding bubbles. Employees of the agency can feed the sheets into a machine which will extract the data and place it in a central database. This saves a great deal of time, as people would otherwise have to manually enter all of this information. These forms are also used in electronic voting in some communities.
Most optical readers are capable of making basic adjustments for user error. For example, a partially filled in bubble will still be recognized. Optical scanning machines are also calibrated to ignore erasures on the sheet; people should use pencil when filling out an optical answer sheet to ensure that they can erase incorrect answers and other accidents. In the case of a graded sheet, if the optical answer sheet is returned to you, it is a good idea to check it over for errors, and to bring these errors to the attention of your instructor so that your grade can be adjusted.