A good distracter should be inferior to the correct answer but should also be plausible to a non-competent candidate.24 All options should be true and contain facts that are acceptable to varying degrees. The examiner would ask for the most appropriate, most common, least harmful or any other feature which is at the uppermost or lowermost point in a range. It needs to be expressed clearly that only one answer is correct. A candidate's response is considered correct if his/her selection matches the examiner's key.15

When creating a distracter, it helps to predict how an inexperienced examinee might react to the clinical case described in the stem.24

Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3410060/