Abstract—The goal of this research is to compare the techniques that estimate and measure the movement time of the right thumb in a curved path on a smartphone according to Fitts’s law. A coordinate randomizing tool was created in this study to randomize the coordinates from the starting point to the target button. The tool was programmed to make an angle of 45-degrees between the starting point and the target button. The experiment was then conducted on 120 Thai university students and the results were analyzed using Mean Absolute Error (MAE) of the estimated or standard movement time. The findings indicated that the technique of measuring distance between buttons using arc length and vertical width has the lowest MAE. The result of this study can be used to improve object placement in user interface and user experience designs.
 

Index Terms—mobile interactions, human-computer interaction, Fitt’s law, button size, gesture, ergonomics