Evaluation of a Text Compression Algorithm against Computer-Aided Instruction (CAI) Material
ELECTRONIC SYSTEMS DIV HANSCOM AFB MA
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INFORMATION STRUCTURED CAI material. The resulting compression ratios are near 1.5 to one for both types of materials. The simulation program was modified to apply the algorithm to the lesson files of a particular frame- structured CAI subsystem used in the Air Force Phase II Base Level System. The compression in this case was found to be 1.3 to one because of the presence in the lesson file of uncompressible, frame formatting bytes. The modified simulation program was also used to take letter occurrence statistics on the text being compressed. From these, a theoretical compression was calculated using a probabilistic model of the compression algorithm. Theoretical compression was within two per cent of measured compression, thus verifying the models applicability.
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