the units, the arithmetic mean of all the output power values has been computed for wind speed intervals of 0.1 m/s. The resulting average curves (thin lines) have been compared with the two estimated power curves (thick dashed lines) corresponding to the lowest (circles) and the highest (squares) air densities provided by the manufacturer (as shown in the right panel of Fig. 3). The fact that each of the mean curves fits between these limiting estimates provides verification that all the turbines were presumably operating correctly and under optimal conditions.