As the coronavirus disease Covid-19 rages in China and spreads to other countries in the world, good estimations of the disease’s epidemiological parameters are crucial to help governments, hospitals, businesses, and the general public to prepare for and to stop the spread of the disease. However, the disease’s fatality rate, one of the most important parameters, is not calculated properly in many government websites and research papers and thus is misleading people’s understanding of the severity of the disease. In this study, we compare various definitions or methods to calculate the fatality rate and point out why they are misleading. We also propose a statistical model to analyze patients’ contraction, recovery, or death process and develop a method to estimate the fatality rate based on available disease statistics.