True.
The mean, or average, is calculated by adding all the values in a dataset and dividing by the number of values. This calculation makes the mean particularly sensitive to extreme values, also known as outliers. For instance, if you have a set of test scores like 70, 75, 80, and 100, the mean would be 81.25. However, if you add an extreme score, such as 200, the new mean jumps to 85. This significant shift illustrates how the mean can be skewed by exceptionally high or low values, making it less representative of the overall dataset when such outliers are present.