Identify the definition of lossy compression.
Mark scheme
- B Data is permanently removed to reduce the file size (1)
- The only correct answer is B. The correct answer is data is permanently removed to reduce the file size.
- A is not correct because the data removed by a lossy algorithm is not restored after transmission
- C is not correct because that describes lossless compression, where the original file is rebuilt exactly
- D is not correct because dictionary encoding is a lossless method that records repeated patterns once
Example answers and how they were marked
Full marks1/1
B Data is permanently removed to reduce the file size
Why: Correct option (1).
No marks0/1
C Data is restored exactly when it is decompressed
Why: Near miss: this describes lossless compression, so no mark.
No marks0/1
A Data is removed only while the file is being transmitted
Why: Misconception that compression only applies during transmission; the data is removed permanently, so no mark.