© 2015 IEEE. The correlation between the set time (tset) and the initial off-state resistance (ROFF) statistics for a Ti/ZrO2/Pt bipolar resistive random access memory device was investigated. The width-adjusting pulse operation method, which can significantly improve the switching uniformity, was used to accurately measure tset, and the gathered statistical data were analyzed using Weibull distributions. Both the Weibull slope (βt) and the scale factor (tset63%) of tset distributions were found to increase logarithmically with ROFF. The observed tset - ROFF interdependence provides a guideline in improving the switching uniformity and optimizing the tradeoff between set speed and disturb immunity. An analytical cell-based model was developed to explain the ROFF-dependent tSET statistics, which can be implemented in statistical compact models and circuit simulators for improving RRAM cell design and memory performances.