Final answer:
The common measure of spread for a normal distribution is the standard deviation, indicating the extent to which data values deviate from the mean.
Step-by-step explanation:
The common measure of spread for a normal distribution is the standard deviation. It is a number that signifies how much the data values deviate from the mean of the distribution. In the context of a wolf's age modeled by a normal distribution, it indicates how varied the ages are around the average age. The larger the standard deviation, the more spread out the ages are. If the standard deviation is small, it implies that the wolf ages are more tightly clustered around the mean.