# meanSquaredError(_:_:) Computes the mean squared error between predicted and ground truth values. ``` @backDeployed(before: macOS 15.0, iOS 18.0, tvOS 18.0, visionOS 2.0) func meanSquaredError(_ predicted: some Collection, _ groundTruth: some Collection) -> T where T : FloatingPoint ``` ## Parameters `predicted` The predicted values. `groundTruth` The ground truth values. The collection must have same number of elements as the predicted values. ## Return Value The mean squared error. ## Discussion Empty collections of predicted and ground truth values will return a value of NaN. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)