To avoid bias, experiments should be performed “blind” with respect to the treatments when possible and particularly when there is any subjective element in assessing the results. After the randomized allocation of animals (or other experimental unit) to the treatments, animals, samples, and treatments should be coded until the data are analyzed. For example, when an ingredient is administered in the diet, the different diets can be coded with numbers and/or colors and the cages can be similarly coded to ensure that the correct diet is given to each cage. Animals can be numbered in random order so that at the postmortem examination there will be no indication of the treatment group. Pathologists who read slides from toxicity experiments are often not blinded with respect to treatment group, which can cause problems in the interpretation of the results.