INDEKS KEMAMPUAN PROSES BERDASARKAN MEDIAN ABSOLUTE DEVIATION; PROCESS CAPABILITY INDICES BASED ON MEDIAN ABSOLUTE DEVIATION

RINDANG NDARU PUSPITA, Sri Hartati

2015 | Skripsi | FMIPA UGM

Process capability indices based on median absolute deviation (MAD) designed to determine of process capability indices for a non-normal data. Process capability is the performance of a process under normal and in-control conditions. Its indices are to measure the inherent variability of a process and thus to reflect its performance. To calculate the capability indices, most industries normally assume that the distribution of their process output is normal. However, in practice, most of process quality control fails the normality test and thus the accuracy of normal based process capability indices becomes doubtful and hence they cannot really reflect the performance of a process. The median absolute deviation is a robust estimate of variability when the sample data are non- normal or are skewed. Real process data and simulated process data from heavily skewed distributions are presented to demonstrate the application of the process capability indices based on median absolute deviation and the results were compared with the indices based on quantile for non-normal and skewed process data. So that the obtained results process capability indices based on MAD is better used for a non-normal data with positive skewness, while process capability indices based on quantile is better used for a non-normal data with negative skewness.

Kata Kunci : capability index; median absolute deviation; non-normal; process data.