What is 'federated learning' and when is it used for privacy-preserving AI?
Federated learning is a distributed training technique where each participant trains on its own local data and only shares model updates—such as gradients or weights—with a central aggregator. This enables a shared model to be improved collaboratively across multiple organizations without exposing sensitive raw data. Because raw data never leaves the local device, the approach provides privacy-preserving collaborative learning. This exactly matches the definition of federated learning.
Why this answer
Federated learning is a distributed machine learning technique where the model is trained across multiple decentralized devices or servers holding local data, without exchanging the raw data itself. Instead, only model updates (e.g., gradients or weights) are shared with a central server, which aggregates them to improve the global model. This approach preserves privacy because sensitive data never leaves the local device, making it ideal for scenarios like healthcare, finance, or mobile keyboard prediction where data cannot be centralized due to regulatory or privacy constraints.
Exam trap
The trap here is that candidates confuse 'federated' with 'federal' or 'government-controlled' systems, or mistake federated learning for simple ensemble methods, when the core concept is decentralized training with privacy-preserving model update sharing.
How to eliminate wrong answers
Option A is wrong because it confuses 'federated' with 'federal' legal systems; federated learning has nothing to do with countries governed by a federal legal structure, but rather refers to a decentralized training architecture. Option C is wrong because it incorrectly implies that a federal government agency controls access to training data; in federated learning, data remains on local devices and is never centrally controlled or accessed by any authority. Option D is wrong because it describes ensemble learning or model combination, not federated learning; federated learning involves iterative collaborative training with shared model updates, not simply combining independently trained models' predictions.