Two problems in test development relate to the use of illustrations: (1) Do illustrated items perform better than written items, and (2) Does item performance vary as a function of the type and size of the illustration? A sample of 63 tests was drawn from all the Air Force Specialty Knowledge Tests containing illustrations. These 63 tests had been administered to approximately 28,261 airmen under operational conditions. Item statistics between illustrated and written items drawn from the same content areas were compared using F ratios. The results indicated: (1) That illustrated items in general performed slightly better than matched written items; (2) That the best‐performing category of illustrated items was tables.

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