TITLE:
Appropriateness of Reduced Modified Three-Parameter Weibull Distribution Function for Predicting Gold Production in Ghana
AUTHORS:
Samuel Kwaku Obeng, Christiana C. Nyarko, Lewis Brew, Kaku Sagary Nokoe
KEYWORDS:
Gold Production, Statistical Distribution Functions, Goodness of Fit Statistics
JOURNAL NAME:
Open Journal of Statistics,
Vol.13 No.4,
August
14,
2023
ABSTRACT: Forecasting
mine production is pertinent to gold mining as it serves as production goals
for investors. It is therefore important to identify the exact distribution
that gold production as a response variable naturally follows. It is even more
appropriate to have a model(s) with few predictor variables. This paper seeks
to identify appropriate statistical distribution functions for fitting gold production in Ghana. The empirical paper
relied mainly on quarterly secondary datasets on gold production between the
years 2009 and 2022 secured from the Minerals Commission of Ghana, Accra.
Several known statistical distributions including Weibull, Log-Normal,
Generalized Extreme Value (GEV) were explored with Maximum Likelihood
Estimation (MLE) and evaluated using model selection criteria as AIC, AICc and
BIC. Goodness of Fits were evaluated using Kolmogorov-Smirnov Test (K-S),
Cramer-Von Mises Statistic and Anderson-Darling Statistic. Based on the
analysis conducted, the reduced modified 3-parameter Weibull distribution
provided the best fit for gold production in Ghana. Though the reduced modified
Weibull function is proposed, it is important however to recognize that other
external factors can influence production levels. Also, the average quarterly fitted gold production
is 1000334.8918 ± 75,327.080 (±7.5%) [i.e.,
925,007.812 – 1,075,661.972]. This indicates that the average annually fitted
gold production lies between 3700031.248 and 4302647.888 ounces at 99.9%
confidence level. Therefore, the predicted gold production for the year 2022 is
3.7million ounces at 99.9% confidence level.