The mean is the average return computed by summing the returns and dividing by the number of investments: 75 / 7 = 10.71%.
The median is the mid-point or central number of returns arranged from highest to lowest or lowest to highest. In this case: 7, 8, 9, 12, 12, 13, 14. The median return is 12%.
The mode is the return that occurs most frequently. In this case, 12% is also the mode.
