Exponential Weighted Moving Average (EWMA) Control Chart for Air Pollution Index at SK Batu Muda, WP Kuala Lumpur

Abstract

Since transboundary haze pollution often occurs and it is a major threat to Malaysia, thus very important for the government to monitor the air quality status from time to time. SK Batu Muda is one of the locations for pollution data observation by Department of Environment Malaysia (DOEM). SK Batu Muda was the most affected location with highest the Air Pollutant Index (API) reading in 2015 compared to year 2016 and 2017, this is considered as anomalies in API reading. To overcome the issue, two types of Exponential Weighted Moving Average (EWMA) control chart are proposed to accurately monitor the air pollution levels in SK Batu Muda named as classical EWMA and iterative re-estimation EWMA. This is to prevent the inflation ofthe control limits which consequently will cause the power to detect changes in the data to be reduced in Phase II. Based on average run length (ARL) results, the iterative re-estimation EWMA control chart in Phase II has tighter control limits compared to classical. As conclusion, the iterative re-estimation EWMA chart is more efficient to handle the anomalous situation for API reading.