QUALITY MANAGEMENT (bpb 44002) Dr. Rosmaini Tasmin Faculty of Technology Management and Business UTHM Johor

Learning Objectives Interpret visual data displays Interpret sample mean, variance, standard deviation and range Concepts of random variable and probability distribution Determine probabilities

Outline Describing Variation Probability Distributions Normal Distributions Statistical Inference for Single Sample

Statistical Process Control Dr. Shewhart 1930’s Small Sample Sizes Bell Laboratories

Statistical Process Control Methodology for charting a process and quickly determines when a process is not in control. Quality is a way of life Doing it right, the first time Is 99.9 % enough? 100 % ~ zero defect Six Sigma means 99.9999998% Motorola Six Sigma means 3.4/1 million

Sample Standard Deviation May the use SD (single event), How about Multiple Events?

Sample Mean Measure of central tendency “Average” value of the data set

Probability Distributions A mathematical model that relates the value of the variable with the probability of occurrence within the population. Value of market share Number of rejects

Normal Distribution The most important distribution in theory and applications of statistics. Normally distributed in a bell curve pattern Symmetrical around the mean 68% 95% 99.7%

Normal distribution 1 time std. dev. 2 time std. dev. 3 time std. dev.

What is VARIATIONS Variations in an observed situation are the fluctuations of recorded data between minimum and maximum with typically a dominant value. There is no two natural objects, are the same. All matters vary, even exact twins…! Two exact model smartphones, also vary.

Distribution Curve at 3 Sigma 3 Sigma level ~ 99.73 % SPC does not eliminate all variations, but identify and separate that special causes of variation

Chance & Assignable Causes of Quality Variation A process that is operating in the presence of assignable causes is said to be an out-of-control process.

Extruder machine

Hamana Extruder’ machines HEMS-01 HEMS-02 HEMS-03 3 exact bunching machines, on production floor, behaves differently.

X-Bar Chart (Practice) N

P-bar chart N Data are the fraction defective of some set of process output

SPC Benefits Alert and Prompt Investigation and corrective action Lessen trial and error Process improvement On the process improvement Control chart shows whether expected results can be achieved Support improvement Continuous The process is in statistical control

Working Process Control Chart

Any question?, if not…