Our objective was to explore the value of considering the number of tasks that use a piece of information when calculating the relevance information has to an operator.

Whereas frequency and criticality of information are often identified as information attributes, the number of tasks that use the information is rarely considered.

We calculated the relevance of pieces of information in air traffic control using criticality and frequency, and compared it to a formula that also considered the number of tasks.

Including number of tasks resulted in information ranking that better accounted for aircraft relevant information, and better supported the information needs of air traffic controllers as determined by judgments of controllers.

The attribute of number of tasks is valuable in calculating the relevance of information.

Interface designers should consider the number of tasks that use a particular piece of information when determining the placement of information within a display.