A closely related, but less common approach is to use binary specifications with 3-level assignment outcomes, in which two different thresholds are set. Depending on how the instructor sets up their specifications grading system, students may only earn credit for an assignment if they meet the higher of the two thresholds , or they may earn credit as long as they meet at least one of the two thresholds . McKnelly et al.'s Writing for Chemists course, described previously, provides an example of the latter case. Grades are bundled based not only on the number of times a student is able to pass a large writing assignment, but also at what passing threshold (a high pass, low pass, or needs revision). For example, students must pass all four writing assignments to earn an A or a B, but for the B grade, students must earn low passes or better on all four assignments, whereas for the A grade students need to earn at least three high passes and may earn only one low pass.