Explain, using an example, how a designer decides which functions of a product should be automatic and which should remain under the user's control. [9]

The decision is based on whether automation gives a safer, faster or more consistent result than a person, while retaining user control where personal preference or judgement is needed.

Functions needing a rapid or consistent response can be automated, for example holding a temperature or cutting power when a fault is detected [2]. These actions may be too slow or unreliable if they depend entirely on a person.

Functions that depend on a user's preference, or on information that the product cannot sense, should remain manual. A product can frustrate users if it repeatedly makes the wrong decision for them [2].

Safety-critical actions should be automatic where delayed human action could have serious consequences. However, a clear and reachable manual override is still needed so the user can take control where appropriate [2].

Cost and complexity also matter: each automatic function needs sensors and control components, and every sensor is another possible failure point [1].

Example: a washing machine can automatically control water level and water temperature because these need consistent measurement and control. The user should still choose the programme because the desired wash depends on the fabric and the user's preference [2].

Judgement: automate repetitive, safety-related control that can be measured reliably; leave choices about the user's intended result under the user's control.