# SQC

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### STATISTICAL QUALITYCONTROL(SQC) :

KHS 1 STATISTICAL QUALITYCONTROL(SQC)

### Slide 2:

KHS 2 What is Quality…??? Quality is a relative term.

### Slide 3:

KHS 3 The 5 Main Dimensions of Quality Pre-determined Standards Reliability Durability Serviceability Performance

### Slide 4:

KHS 4 What is Quality Control ? Maintaining pre decided standards of the products.

### Slide 5:

KHS 5 What is STATISTICAL Quality Control? Statistical techniques used for Controlling or Maintaining “ Pre-determined Quality”.

### Slide 6:

JBS 6 Any two Products never be same in all aspects. This difference is called “VARIATION”.

### Slide 7:

JBS 7 Causes of Variation: Due to Man, Machine, Material, Time and so on…

### Slide 8:

JBS 8 Types of Variations: Assignable Causes : Chance Causes :

### Slide 9:

MAS 9 Chapter 1 9 Introduction to Statistical Quality Control, 6th Edition by Douglas C. Montgomery. Copyright (c) 2009  John Wiley & Sons, Inc.

### Slide 10:

MAS 10 Shewart Control Charts: The distribution of Statistic (T) is assumed to be Normally Distributed.

MAS 11

### Slide 12:

MAS 12 99.73% of observations lie in μ ±3σ. LCL = (Mean of T) – 3(S.D. of T) CL = (Mean of T) UCL = (Mean of T) + 3(S.D. of T)

### Slide 13:

MAS 13 CL UCL LCL Control Charts: * * * * * * * * * * * *

### STATISTICAL BASIS OF CONTROL CHART :

KHS 14 STATISTICAL BASIS OF CONTROL CHART

MAS 15

### Slide 16:

KHS 16 Types of Control Charts : _ Charts for Variables : X , R Charts for Attributes : p, np, c

### Slide 17:

KHS 17 Charts for Variable : X bar chart monitors the between sample variability R chart monitors the within sample variability.

### Slide 18:

KHS 18 Here, n = Number of units in the sample = 5 m = Number of samples = 25

KHS 19 R =

KHS 20

KHS 21

### Control Limits for Chart :

KHS 22 Control Limits for Chart depends on value of n.

### Control limits for R Chart :

KHS 23 Control limits for R Chart D3 and D4 are depend on value of n.

JBS 24 EXAMPLE 1

JBS 25

### Slide 26:

JBS 26 UCL CL LCL R 25.17 22.5 19.83 9.71 4.6 0 X-bar and R Control Chart Limits

JBS 27

### Slide 28:

JBS 28 X-bar & R Chart Interpretation X-bar chart indicates that no point is above UCL OR below LCL. R-bar chart indicates that no point is above UCL OR below LCL. So, Process is considered as under control.

### Slide 29:

MAS 29 Example 2 Sample X-bar R Sample X-bar R Sample X-bar R 1 55.6 22 11 51.2 15 21 50.0 11 2 61.0 23 12 49.4 14 22 47.0 14 3 45.2 20 13 44.0 32 23 50.6 15 4 46.2 11 14 51.6 14 24 48.8 16 5 46.8 18 15 53.2 12 25 44.6 22 6 49.8 23 16 52.4 23 26 46.8 16 7 46.8 18 17 50.6 8 27 49.2 8 8 44.2 20 18 56.0 18 28 45.6 19 9 50.8 32 19 50.2 19 29 57.6 40 10 48.4 16 20 44.0 23 30 51.4 17

### Slide 30:

MAS 30 Summary Information

### Slide 31:

MAS 31 UCL CL LCL R 60.38 49.63 38.89 39.40 18.63 0 X-bar and R Control Chart Limits

MAS 32

MAS 33

### Slide 34:

MAS 34 X-bar & R Chart Interpretation X-bar chart indicates that one point is above the UCL (at sample 2). R chart indicates that one point is above the UCL (at sample 29). So, Measures would be investigated to reduce process variation at that point.

### Control Limits, Specification Limits, and Revised Limits :

MAS 35 Control Limits, Specification Limits, and Revised Limits Control limits are functions of the natural variability of the process Specification limits are determined by developers/designers

### Control Limits, Specification Limits, and Revised Limits :

MAS 36 Control Limits, Specification Limits, and Revised Limits Revised limits are the limits for the future production There is no mathematical relationship between control limits and specification limits.