Parameters and are constants that can be empirically determined. Based on the information in [3], we assume to be and to be .

The Hick-Hyman Law can be useful only if the number of different
choices, , is known. Unfortunately, it is hard or even
impossible to estimate for many cognitive processes. A menu
selection may actually involve more choices for a user than the
number of menu items because the user may evaluate the consequence
of selecting an item and the possible subsequent choices to decide
whether to select that item or not. In this study, we
conservatively assume to be the number of most direct choices
like the number of menu items and the number of buttons to choose
from.

Lin Zhong 2003-12-20