The four measures and their formulas
The mean is the arithmetic average: add all values and divide by the count. It accounts for every number in the set, which makes it sensitive to extreme values. A single very high or very low value can pull the mean far from where most data points sit.
The median is the middle value when all numbers are sorted in order. For an odd count, it is the single middle number. For an even count, it is the average of the two middle numbers. Because the median depends only on position, it is not affected by extreme outliers.
The mode is the value that appears most frequently. A dataset can have one mode, multiple modes, or no mode at all if every value appears exactly once. Mode is most useful for categorical or discrete data where you want to know the most common outcome.
The range is the difference between the maximum and minimum values. It describes spread in its simplest form. A large range indicates high variability; a small range suggests the values are clustered closely together.
Mean = Sum of values / Count of values
Add all numbers together and divide by how many there are to get the arithmetic mean.
Median = middle value of sorted list (or average of two middle values)
Sort the values in order. For an odd count, take the centre value. For an even count, average the two centre values.
Mode = value(s) with the highest frequency
The mode is the number that appears most often. If no value repeats, there is no mode.
Range = Maximum value - Minimum value
The range shows how spread out the data is by measuring the gap between the largest and smallest values.