NCIDQ Interior Design Professional Exam (IDPX) Practice Exam 2025 - Free Interior Design Practice Questions and Study Guide

The efficiency factor of a single leased space is effectively represented by the ratio of the net area (or net assignable area) to the usable area. This concept is critical in understanding how much of the leased space is effectively utilized for the tenant’s activities, as opposed to the space that is common or shared among tenants.

The efficiency factor calculation highlights how well a space is organized and whether it meets the tenant's functional requirements within the confines of their lease. A higher efficiency factor indicates that a larger portion of the total area is usable for specific tenant functions, revealing a more efficient use of space compared to common areas.

The other options do not address the concept of efficiency in a way that captures the relationship between the various types of areas involved. Rather, they focus on aspects like accommodating specific functions or determining space requirements per person, which do not directly measure the relationship of usable space to overall square footage. Thus, focusing on the net area compared to usable space provides the most accurate depiction of efficiency in a leased space context.