EFFECTS OF TRAINING AND EXPERIENCE Petty (1974) showed that, although LGD experience did not significantly affect performance ratings, previous training did. Individuals who received a 15-minute briefing on the history, development, rating instruments, and research relative to the LGD were rated significantly higher than untrained individuals. Kurecka, Austin, Johnson, and Mendoza (1982) found similar result results and showed that the training effect accounted for as much as 25 percent of criterion variance. To control for this, either all individuals trained in the LGD can be put into the same group(s), or else the effects of training can be held constant statistically. One or both of these strategies are called for in order to interpret results meaningfully and fairly.