Despite the above limitations, the scheme of complexity factors developed for numeracy assessment in ALL comprises a theoretical contribution. It provides a conceptual basis for predicting the different levels of complexity of a broader range of items well beyond those involving arithmetic operations only. To the extent these predicted difficulty levels later prove to correlate with actual difficulty (such as in terms of percent correct on different items), this scheme can also assist in interpreting survey results, as it can help to explain why some items are harder than others and what kinds of cognitive processes are called for by different tasks.

Indeed, results from the feasibility and pilot studies described later in this report show that predicted difficulty and observed difficulty were highly correlated. Nonetheless, further distillation and validation are needed, and the scheme in its current state is included mainly to show the logic behind a process used during item development.