This specification discloses a computer program product for creating print data utilized by an ink jet printer. The ink jet printer comprises an ink jet head moving in a predetermined direction with respect to a print medium. The computer program product includes instructions for ordering a computer to perform a reading step of reading image data that includes a plurality of first combinations. Each first combination comprises a position and information concerning whether a dot is to be formed at the position. The computer program product includes instructions for ordering the computer to further perform a print data creating step of creating the print data by creating a second combination for each position at which the dot is to be formed. Each second combination comprises the position at which the dot is to be formed and one nozzle randomly selected from the nozzles of the nozzle unit which corresponds to the position. In the print data creating step, the same nozzle cannot be selected for more than a predetermined number of positions continuously aligned along the predetermined direction.