Process capability evaluation of a product

Wu, Chin-Chuan; Chen, K. S.; Kuo, Hsin-Lin

doi:10.1080/02522667.2003.10699582

Cited by 1 publication

(3 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Because a Cpk index is an aggregate value, calculated from individual moisture measurements in the experiment, many replicates of experiments were needed to ensure that values of Cpk index used for analysis have good precision. Approximating a minimum number of samples to acquire a specific confidence bounds are discussed in Wu and Kuo (2004). In the paper, sample size for Cpk are estimated using Bissell's approximation (Bissell 1990).…”

Section: Ii4 Finding Minimum Sample Size For Cpk Approximationmentioning

confidence: 99%

“…There are caveats for these approximations in that minimum number of samples are required for the approximated values to be accurate. Bissell's approximation of confidence interval (Bissell 1990), which forms the basis of Cpk approximation in Wu and Kuo (2004), suggests that the normal approximations in the paper would be accurate only when it is calculated using at least 50 samples. Lewis (1991), which explores effects of sample size in process capability index calculation, also reports that estimation of Cpk cannot be sufficiently reliable when sample size is under 50 because the random errors would be greater than 18%.…”

Section: Ii4 Finding Minimum Sample Size For Cpk Approximationmentioning

confidence: 99%

“…Lewis (1991), which explores effects of sample size in process capability index calculation, also reports that estimation of Cpk cannot be sufficiently reliable when sample size is under 50 because the random errors would be greater than 18%. On the contrary, Wu and Kuo (2004) suggests a less stringent minimum sample size at 30 samples. Many of the values in Table II.4 that require less than 50 samples (denoted with asterisks) are less reliable in estimating values of Cpk.…”

Section: Ii4 Finding Minimum Sample Size For Cpk Approximationmentioning

confidence: 99%

See 2 more Smart Citations

Post-roast Moisture Process Improvement of Fish Sheet Production Process

Jitapunkul

View full text Add to dashboard Cite

The primary concern of this thesis is moisture control of fish sheets produced in a Thai factory. The moisture control of fish sheets is important because these fish sheets are primary work-in-process products used in the factory, and the sheets’ post-roasting moisture is a key quality metric for fish sheets. The factory initially used ad-hoc subjective procedures to control moisture level. However, it is found that variation of fish sheets’ moisture at all stages of production remains high, making it a subject of process improvement in this thesis. The Cpk index of post-air-drying and post-roasting fish sheets, measured at the start of the project, are 0.19 and 0.04 respectively. This report will present and evaluate two process improvement methods implemented in the factory. The first method modifies ingredient mixing procedures such that the quantity of water in ingredient mixture are adjusted based on measured moistures of frozen minced fish which is the primary non-water ingredient in the mixture. To avoid subjective adjustment of control parameter values, the second improvement finds an optimised set of values for post-mixing processes’ parameters, using response surface generated with regression analysis on data collected in a design of experiments. After improvement, the post-air-drying Cpk index and the post-roasting Cpk index were improved to 0.75 and 0.46 respectively.

show abstract

Section: Ii4 Finding Minimum Sample Size For Cpk Approximationmentioning

confidence: 99%