A method of extracting an optimized digital variable resistor (“DVR”) value of a display panel, the method including varying a DVR value, corresponding to a common voltage, and applying the varied DVR values to the display panel, measuring brightness values of the display panel for at least two frames, extracting flicker values corresponding to the varied DVR values using the brightness values, and extracting an optimized DVR value by generating first to third coordinate values in which coordinate values have x-coordinate values and y-coordinate values representing DVR values and flicker values, respectively, calculating a first linear function of a first straight line connecting two of the coordinate values, and a second linear function of a second straight line using the first linear function and the other of the coordinate values, and extracting an x-coordinate value at an intersection point of the first and second lines, as the optimized DVR value.