Scantron machines are optical mark recognition (OMR) devices used to grade multiple-choice tests. They work by scanning the test form and detecting the presence or absence of marks in specific locations. These locations correspond to the answer choices for each question.
To ensure accurate scanning, Scantron machines require pencils that produce marks that can be easily detected. Number 2 pencils (also known as HB pencils) are the most commonly recommended type of pencil for use with Scantron machines because they produce dark, consistent marks that are easily recognized by the scanner.
Other types of pencils, such as mechanical pencils or pencils with soft lead, may not produce marks that are dark enough or consistent enough to be accurately scanned by the machine. This can lead to errors in grading, such as marks being missed or incorrectly interpreted.
In addition to using a number 2 pencil, it is important to follow the instructions on the test form when filling it out. This includes marking the answer choices clearly and avoiding stray marks or smudges, as these can also interfere with the scanning process.