What should you use to minimize the effect of one or more extreme values an average score?

To minimize the effect of one or more extreme values (outliers) on an average score, you should use the median instead of the mean (average).

The mean is highly sensitive to outliers, as it takes into account every single data point. The median, on the other hand, represents the middle value when the data is ordered, making it robust to outliers. The extreme values have less impact on the median's position.