Suppose we solve a linear program ``by hand'' ending up with an optimal table (or tableau to use the technical term). We know what an optimal tableau looks like: it has all non-negative values in Row 0 (which we will often refer to as the cost row), all non-negative right-hand-side values, and a basis (identity matrix) embedded. To determine the effect of a change in the data, we will try to determine how that change effected the final tableau, and try to reform the final tableau accordingly.