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Statistical Methods for Biotechnology Products
Part I: Biopharmaceutical Product Statistical Quality Control by Professor, Jen-pei Liu, PhD, Professor Division of Biometry, Department of Agronomy National Taiwan University, and Division of Biostatistics and Bioinformatics National Health Research Institutes 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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Statistical Quality Control
1. Introduction 2. Concept 3. Simple Graphical Techniques 4. Control Charts and R Charts 6. Process Capability 7. P Charts 8. C Charts 9. Six Sigma Concept 10. Summary 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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1 Introduction Total Quality Control (TQC) Malcolm Baldridge Award
Products or service of the highest quality Avoid defective products Avoid customer complaints Malcolm Baldridge Award 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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2 Concepts Single Process Process Output Inputs
2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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2 Concepts Breakdown of a product or service into a series of interrelated subprocesses 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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From: Cronin, et al (Clinical Chemistry, 2004)
2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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2 Concepts Statistical Process Control (SPC)
The use of statistical quality control techniques is called statistical process control 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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2 Concept Detection Approach to Quality Control
2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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2 Concept Prevention Approach to Quality Control
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2 Concept Costs of Inspection vs Cost of Undetected Defects
2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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2 Concepts The control chart is based on sample information, measurable or qualitative from the process at different point in time Control charts for variables(measurable quantity) Control charts for attributes(attribute data) Costs of Inspection vs cost of undetected defects 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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2 concepts On-line quality control technique - control charts
Off-line quality control technique - Experimental design - Taguchi methods for optimizing the process to set level key process variables for yielding the highest possible quality 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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3 Simple Graphical Techniques
Specification Limits : A variable should be if it is to meet function and quality standards The largest allowable value of a variable is called the upper specification limit(USL) and the lowest allowable value is the lower specification limit(LSL) 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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3 Simple Graphical Techniques
Example: Copper thickness of 50 printed circuit board Specification: 0.001~0.003 in. 26/50(52%) not meet specification 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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3 Simple Graphical Techniques
A Pareto chart is a bar chart where each bar is associated with a particular area of concern and the bars are drawn, from left to right, in order of decreasing height PC Rejection DATA Type of Defect Number of Rejected Boards Poor electroless coverage Lamination problems Low copper plating Plating separation Etching problems Miscellaneous 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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3 Simple Graphical Techniques
Pareto Chart 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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3 Simple Graphical Techniques
The fishbone diagram is a graphical way of displaying the possible reasons, or causes, of a particular problem The fishbone diagram is called the cause-and-effect diagram 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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3 Simple Graphical Techniques
Construction of a cause-and-effect diagram 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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3 Simple Graphical Techniques
A cause-and-effect diagram 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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4 Control Charts To differentiate controlled variable-assignable causes from uncontrolled variables-chance variation (W.A. Shewhart,1931) 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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4 Control Charts Example of assignable causes: types of raw materials used, differences in workers used, slow wearing down of the machinery, changes in temperature or humidity Statistical Control: When all the assignable causes have been found and eliminated,a process is then said to be statistical control 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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4 Control Charts A typical Control Chart
2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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4 Control Charts Centerline:grand average of all the sample statistics
Lower and upper Control Limits: Determined by the sampling distribution and are positioned 3 standard deviations above and below the centerline Out of Control: Points outside the control limits In control: Points within the control limits 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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4 Control Charts Classification of Control Charts
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4 Control Charts Difference between Control limits and specification limits 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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5 and R Charts The Chart monitors the means of small samples taken from a process The R Chart monitors the range(or variability) of small samples taken from a process The Control Limits of the Chart are computed by using the centerline of the R chart The Chart should not be used without constructing the corresponding R Chart 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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5 and R Charts Data Sample Number 1 2 ………. K Sample Size n n ……… n
Sample mean …… Sample Range R1 R2 ……. Rk k=20 to 25 , n=3 , 4 or 5 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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5 and R Charts The R Chart Centerline: Upper control limit UCL=D2
Lower control limit LCL=D1 D1and D2 depend on sample size n and can be found in table If n 6; D1= LCL=0 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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5. and R Charts Product: Precision ball bearings
Characteristic: bearing diameter Target value: in. Specification Limits: in. Data: Hourly measurements of 5 learning diameters (x1000) from the target value 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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5 and R Charts 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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5 and R Charts N=5 K=25 R=6.56 in. D2=2.115 D1=0
UCL=D =(2.115)(6.56)=13.874 LCL=D =(0)(6.56)=0 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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5 and R Charts R Charts for ball bearing diameters
2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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5 and R Charts Charts Centerline: Upper Control limit: UCL=
Lower Control limit: LCL= A: depends upon the sample size and can be found in Table 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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5 and R Charts Example: K=25 n=5 =0.048 =6.56 A1=0.577
UCL=0.048+(0.577)(6.56)=3.83 LCL= (0.577)(6.56)=-3.74 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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5 and R Charts Chart for ball bearing diameters
2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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1. Most sample means are scattered at random around the central line
2. A few sample means spread out and are close to either the lower or upper control limit. 3. No sample mean is outside the control limits. 4. No recognized pattern of the distribution of sample means is observed. 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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1. A sample mean is outside the control limits 3
The probability of this event under normality assumption is about In general, from Chebyshev's inequality, there is a probability of 0.11 that a sample mean is outside the three standard deviation control limits (or action limits). 2. Under normality assumption, the probability of two out of three consecutive means outside two standard deviation warning limits is 3(0.05)2(0.95) = 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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3. Eight consecutive sample means are on the same side of the central line. The probability of this event for any distribution symmetrical about the population mean is 4. Sometimes, it is also worthwhile noticing that four of five successive sample means are outside the one standard deviation limits because that probability of this event under the normality assumption is given by 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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5. In many cases, samples collected from two or
more underlying distributions are combined together for construction of control chart. An unnatural pattern of all sample means scattering around the central line with unnaturally small fluctuations will occur. This type of control charts is invalid because samples from different distributions have been combined. This phenomenon is referred to as stratification. 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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6. If half the samples come from one distribution and the other half come from another distribution, the sample means will scatter within the control limits rather than concentrate on the central line. This phenomenon is called mixture. 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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7. The existence of a trend for a manufacturing process can be identified by the following unnatural patterns: (a) One sample mean outside the control limits on one side is followed by the next consecutive sample mean, which is outside the control limits on the other side. (b) There are at least six consecutive sample means, one of which is greater (or lower) than the previous one. 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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8. The presence of a systematic variable in the process is suggested if at least eight consecutive sample means alternate large, small, large,and small without interruption. This pattern may occur when samples are selected alternately from different operators or machines. 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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6 Process Capability Process capability refers to the ability of a process to stay within its specification limits Actual process spread: Under normal assumption,all measurements generated by the process should be within a range of 6 Allowable process spread: The distance between the specification limits 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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6 Process Capability The process capability index is defined by
Where is the SD of measurements from the process A cp Continue to maintain B cp < Improve to A C cp < Improve at once D cp < Consider stopping product E cp < Stop production at once 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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6 Process Capability 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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6 Process Capability 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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6 Process Capability The Cpk Index Min=minimum K-factor :
The relationship between cpand cpk Cpk=Cp(1-k) 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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6 Process Capability Data:Ball bearing diameters
Target value: USL=10 LSL=-10 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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Cpk=Cp(1-k)=(1.182)( )=1.176 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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7 The P-Chart A control chart for controlling the percent of defectives in a sample is called a P chart Sample Number … k Sample Size n1 n2 … nk # of defectives x1 x2 … xk % of defective 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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7 The P-Chart Centerline : Upper control limits UCL=
Lower control limits LCL= 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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7 The P-Chart # of rejected circuit boards
2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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7 The P-Chart Since =0.054 and =305(given in table 16.11),the average sample size method gives control limits of or or 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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7 The P-Chart Average Sample Size
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7 The P-Chart Variable Sample Sizes
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8 The C-Chart A C-chart is used when the objective is to control the number of defects per unit A defective item may have more than one defect A defect is just a flaw or nonconformity To monitor defects requires determination of the inspection unit Example: Accounting records: # of error per 10 records Sheet metal:surface flaws in 1 square foot 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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8 The C-Chart (Poisson Distribution)
Inspection unit 1 2 …K #of defects C1 C2…Ck Centerline: Upper Control limit UCL= Lower Control limit LCL= 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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8 The C-Chart The Data of Solder Defects
2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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8 The C-Chart 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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8 The C-Chart Solder Defects
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9 Six Sigma Concept A management method to pursue excellence in quality Improvement in manufacturing capability Eliminate waste in manufacturing process Improve manufacturing quality 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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9 Six Sigma Concept The usual concept
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9 Six Sigma Concept The concept 1.5 off the target value
2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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9 Six Sigma Concept 製程命中目標與偏離目標1.5 缺點之對照表
製程命中目標與偏離目標1.5 缺點之對照表 PPM : Part per Million; Source: Pan and Lee (2003) 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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9 Six Sigma Concept Motorola(1987) started six sigma program
Won the Baldridge award in 2 years A five-fold growth between 1987 and 1997 A 20% profit increase per year A reduction of 14 billion USD in cost Allied Signal(1991) GE(1995) Application to all different business 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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9 Six Sigma Concept Source: Pan and Lee (2003) 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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10 Summary Graphical Techniques Charts R Charts P Charts C Charts
Process Capability Six Sigma 2018/11/21 Copyright by Jen-pei Liu, PhD, Products are just for illustrations only
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