Modeling the Number of Confirmed Cases of Covid-19 in East Java Using Negative Binomial Regression Based on Least Square Spline Estimator

The East Java Province has experienced a significant surge in number of confirmed cases of COVID-19. This study endeavors to investigate the potential correlation between weather conditions and the incidence of number of confirmed cases of COVID-19 in East Java. To achieve this, a nonparametric regression model, specifically, the Negative Binomial Regression (NBR) model based on the least squares spline estimator, was utilized. The outcomes of the study indicate that the Mean Absolute Percentage Error (MAPE) of nonparametic regression model is 0.30. Meanwhile, the MAPE for the parametric regression model is 0.34. The results show that a nonparametric regression model approach is better than parametric regression model approach. The study establishes that the truncated spline estimator based NBR model represents the best fit, with an MLCV value of -256.71. The findings of the study suggest that a temperature less than 21.75ºC is associated with a decrease of 13.28 number of confirmed cases of COVID-19 per each 1ºC increase, while a temperature between 21.75ºC and 25.78ºC is linked to an increase of 6.85 number of confirmed cases of COVID-19 per each 1ºC increase. In contrast, a temperature greater than 25.78ºC is associated with a decrease of 139.42 number of confirmed cases of COVID-19 per each 1ºC increase. Similarly, a wind speed less than 5.57 m/s is related to a decrease of 12.99 number of confirmed cases of COVID-19 per each 1 m/s increase, whereas a wind speed between 5.57 m/s and 8.99 m/s is associated with a decrease of 10.29 number of confirmed cases of COVID-19 per each 1 m/s increase. Furthermore, a wind speed greater than 8.99 m/s is linked to a decrease of 19.16 number of confirmed cases of COVID-19 per each 1 m/s increase. The study provides evidence that higher temperatures and wind speeds result in a slower rise in the incidence of the number of confirmed cases of COVID-19. Consequently, it is recommended that the local government remains vigilant during periods of low temperature and wind speed, which may result in a more rapid increase in the number of confirmed cases of COVID-19.