Final answer:
The median is the middle value in an ordered data set, different from the mean, which is affected by outliers. Unlike the mean, the median is unaffected by extreme values. A data set may have more than one mode if multiple values occur most frequently.
Step-by-step explanation:
The statement that the median is calculated by adding all values in a data set and then dividing by the number of values is incorrect. This describes the mean, which is the arithmetic average of a set of numbers. The median is the middle value in an ordered data set that divides it into two equal halves. It is resistant to the influence of outliers and extreme values, making it a suitable measure of center in such situations. On the other hand, the mean is sensitive to extreme values and can be significantly affected in small data sets with such outliers.
Moreover, the claim that there can be only one mode in any given set of data is incorrect. A data set can have multiple modes, which occurs when two or more values have the same highest frequency; such a data set is referred to as bimodal or multimodal.