Final answer:
The key feature missing from Custer Manufacturing's information system is that it's not understandable. The employees cannot easily utilize the system, leading to inefficiencies and increased costs, highlighting the importannce of user-friendly design in information systems.
Step-by-step explanation:
In the scenario with Custer Manufacturing's new information system, the characteristic of useful information that is clearly absent is E) Understandable. Employees find the new system confusing and are unable to use it effectively to plan production, which indicates that the information presented is not easily digestible or interpretable by the average user. While the system was intended to streamline access to mission-critical information and improve production efficiency, it instead resulted in decreased productivity due to its lack of user-friendliness. This illustrates the importance of ensuring that end-users can comprehend and utilize the provided information in order for it to be considered useful.