In the present paper, we discuss about design methodology to study the reliability of a microelectromechanical systems device. The proposed methodology was illustrated for design of a comb-drive actuator. In particular, effect of variations introduced in the design parameters due to the fabrication process and their impact on reliability of a comb-drive actuator is reviewed in detail. We use Crystal BallÂ® (Decisioneering, Inc., 2000), a probabilistic analysis tool to analyze the performance of comb-drive actuator. The present method requires an analytical model or transfer function derived using experimental data to study the variation in output due to variations in input parameters. We developed an analytical model for displacement of actuator and verified the analytical model using finite element model. This analytical model was used to study the variation in displacement of comb-drive actuator. This methodology uses a combination detailed experimental studies done to establish fabrication limitations or capabilities. The analysis and final design selection was based on a combination of Crystal BallÂ® studies and fabrication constraints. The same methodology could be extended to study the reliability of MEMS sensors and actuators due to variations on process parameters.