To test reaction times, a computer program will display a red circle. When the red circle changes to yellow, the users click the mouse as fast as possible. The program will then display the reaction time. Students want to compare reaction times between people using their dominant hand and nondominant hand on the mouse.Suppose $20$ subjects were participating in this study. Describe how the study would be conducted with a paired design with repeated measures.

If a significant difference in reaction times is found, can the conclusion be made that the hand being used caused the difference?