Appropriate Model Identification Using Turn Around Time of Vessels at Tincan Island Port, Lagos, Nigeria

Abstract

This study applies the Buys-Ballot procedure to decompose and analyze the monthly turnaround time of vessels at Tincan Island Port, Lagos, Nigeria, covering the period from 2015 to 2024. The primary objective is to identify the appropriate time series model—additive, multiplicative, or mixed that best represents the data structure and seasonal behavior of vessel turnaround operations at the port. Monthly data comprising 120 observations were arranged into a Buys-Ballot table, and both graphical and statistical analyses were conducted to estimate trend parameters and seasonal indices. The Levene’s test of equality of variances was employed to determine the correct decomposition model. Results indicated that the computed Levene’s test statistic (0.264) was less than the critical value (1.91) at the 5% level of significance, leading to the acceptance of the null hypothesis of equal variances. Consequently, the transformed data admit an additive model. The study concludes that the Buys-Ballot procedure is a simple and effective method for identifying suitable models in descriptive time series analysis.