with G corresponding to the grouping variable, "r" the reference group, and "f" the focal group. This equation represents an instance where DIF is not present. In this case, the absence of DIF is determined by the fact that the conditional probability distribution of Y is not dependent on group membership. To illustrate, consider an item with response options 0 and 1, where Y = 0 indicates an incorrect response, and Y = 1 indicates a correct response. The probability of correctly responding to an item is the same for members of either group. This indicates that there is no DIF or item bias because members of the reference and focal group with the same underlying ability or attribute have the same probability of responding correctly. Therefore, there is no bias or disadvantage for one group over the other.