A file that has undergone which type of compression is likely to have a smaller file size but lower quality?

The answer is indeed lossy compression. This type of compression reduces file size by permanently removing certain data from the file, which can lead to a decrease in quality. It is commonly used in formats like JPEG for images or MP3 for audio, where a balance between file size and quality is often desired.

Lossy compression works by eliminating information that is considered less critical, thereby significantly decreasing the file size. For example, in audio files, frequencies that are beyond the human hearing range might be removed. While this results in smaller files that are easier to store and share, it comes at the cost of some fidelity in the original content.

In contrast, lossless compression retains all original data and allows for the complete restoration of the file to its original state, which means the quality remains intact even though the file size is reduced. Uncompressed files, naturally, have no reduction in size or quality, as they store all data in its original form. Optimized compression can refer to a variety of techniques and might include both lossy and lossless methods, but it does not inherently imply a reduction in quality like lossy compression does.