Studies into this field were initially done by Stuart K. Card, Thomas P. Moran, & Allen Newell in 1983.
[1] Current studies in the field include work to distinguish process times in older adults by Tiffany Jastrembski and Neil Charness (2007).
The calculations depend on the ability to break down every step of a task into the basic process level.
The following formula can be used to find the probability: P = e-K*t where K is the decay constant for the respective memory in question (working or long term) and t is the amount of time elapsed (with units corresponding to that of K).
It is important to deduce beforehand whether the user would be able to repeat the vital information throughout time t, as this has a negative impact on the working memory if they cannot.