การทดสอบค่าสัมประสิทธิ์การแปรผันของปริมาณฝุ่นละอองขนาดเล็ก (PM2.5) ของอำเภอหาดใหญ่ จังหวัดสงขลา

บทคัดย่อ

The biggest impact of particulate air pollution on public health is understood to be from long-term exposure to fine particulate matter (PM2.5), which increases the age-specific mortality risk, particularly from cardiovascular causes. Usually, the hourly PM2.5 level fits a gamma distribution, and this has led us to consider testing this via the coefficient of variation (CV) of these data. Herein, we present two statistical methods for testing the CV in a gamma population based on the Score and Wald methods. To compare their performances, a simulation study was conducted under several shape parameter values for a gamma distribution. The performances of the test statistics were compared based on their empirical type I error rates and powers of the test. Their performances were then illustrated by applying them to the hourly PM2.5 level in Hat Yai, Songkhla, Thailand. The simulation results show that the test statistic based on the Wald method performed better than the one based on the Score method in terms of the attained nominal significance level and is thus recommended for analysis in similar scenarios.

Keyword: Hypothesis testing, Measure of dispersion, Gamma distribution, Air pollution