Final answer:
The variance function is used to determine the spread of data within a group, which quantifies how much the data points deviate from the mean(option b).
Step-by-step explanation:
The function used to determine how widely data are spread out within a group is the b)variance.
The variance, along with the standard deviation, is a statistical measure that represents the degree of spread or dispersion of a set of data points. The standard deviation—a number that measures how far data values are from their mean—is the most common measure of variation or spread. When calculating the variance or standard deviation, different formulas may be used depending on whether the data represents a sample or the entire population.