Test of the Randomness of Residuals and Detection of Potential Outliers for the Morgan-Mercer-Flodin Used in the Fitting of the Prediction of Cumulative Death Cases in Nigeria Due to COVID-19

Abstract

In this study, we use the Wald–Wolfowitz runs test as a statistical diagnosis tool to check whether the randomness of the residual for the Morgan-Mercer-Flodin (MMF) utilized in the fitting of the prediction of cumulative death cases in Nigeria owing to COVID-19. The runs test revealed that there were 13 total runs, however the number of runs that should have been expected based on the randomization assumption was 26. Because the p-value was less than 0.05, we can conclude that the residuals are not truly random and must reject the null hypothesis. Too many instances of a specific run sign may indicate the presence of a negative serial correlation; on the other hand, too few runs may indicate the presence of a clustering of residuals with the same sign or the presence of a systematic bias. A further analysis of the residuals using the Grubb's test indicate the existence of an outlier, which indicates that the data must be remodeled because of the presence of the outlier.