Fixing Usability Problems Early – the Cost of Delay
In 1996 Prasad published data from the automotive industry (see graph), showing that the costs of fixing mistakes grows relentlessly as you get closer to market. This relationship has been found in other industries too, including manufacturing, banking and transport. There’s no reason to think that medical devices is any different in this regard.
And fixing a mistake once you are on the market is the most expensive option of all. Not only that, but your ability to control the change process recedes as you approach launch.
And of course, once your product is on the market you have ceded much control to your customers, competitors, regulators, lawyers etc. The market is an unforgiving place in which to fix usability problems. Much better to have done so before you expose your product to the market.
Finding usability problems early, and fixing them in the formative phase is the most cost-effective way to do it. In our experience, almost all of the usability problems seen during validation could (and should) have been identified and designed out during the formative phase.
The sweet spot for fixing design problems is during the design verification phase – because the costs are containable and you have maximum control. Design verification processes include formative usability evaluations, and they are an essential part of the human factors program.