3.4. Model validation

This simulation is based on the following settings: the initial time is March 1, 2021, the time step is 1, and the unit is a day. The purpose of validation is to prove the reliability and credibility of the model, and to evaluate the ability of the model to reproduce historical data. For historical verification, this study selected vaccinated population, total death, and total infection as the primary variables, and compared the historical data with the model simulation results (Figs ​(Figs22–4).

Based on Barlas [64], a system dynamics model will be valid if the error rate is less than 5%. Since system dynamics simulates over time, Mean Absolute Percentage Error (MAPE) is used to calculate the error rate. The equations are shown in Eqs 5 and 6, withN being number of data, A actual data, and S simulation data. The result is shown in Table 2. All MAPE values show that system dynamics fulfills validation criteria with an error rate of less than 5%. Also found is that the overall variation trend is consistent when the simulation is run under the basic conditions and scenarios. Therefore, the simulation results are acceptable and the SIRD model can provide reasonable output behavior.