Single Ended vs Double Ended Design Constraints
The design of the door would be an example of a single-ended design constraint, because it imposes a limitation on one end of the range of characteristics being considered. For example, if the doorway is designed to accommodate people of 95th percentile height, that door would also accommodate everyone shorter than this.
This can be contrasted with a double-ended design constraint. Double-ended constraints need consideration of both ends of the distribution of the parameter. For example, if we were designing a cycle helmet (or a product where exact fit is important) we would need to consider both the largest and smallest anticipated head circumference. If we just considered the 95th percentile head circumference, the helmet would not fit properly (i.e., be too big and therefore exclude) for smaller users.
Test your understanding of single-ended vs double-ended design constraints by completing the true or false quiz below.