Statistical quality control, sampling
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The document discusses various quality control tools used to identify issues, analyze causes, and monitor processes. It provides descriptions and examples of seven key QC tools: Pareto diagram, cause-and-effect diagram, histogram, scatter diagram, check sheet, control chart, and graph/flow chart. These tools can help objectively assess situations, identify problem areas, determine relationships between factors, and maintain process stability. The document emphasizes that collecting data and practicing the use of these tools is important for effectively solving problems and improving processes.
![When is it used and what results will be obtained?
Which is the most serious problem among many problems? It is mainly
used to prioritize action.
Usage Results
•Used to identify a problem.
•Used to identify the cause of a
problem.
•Used to review the effects of an
action to be taken.
•Used to prioritize actions.
[Used during phases to monitor
the situation, analyze causes, and
review effectiveness of an action.]
•Allows clarification of
important tasks.
•Allows identification of a
starting point (which task
to start with).
•Allows projection of the
effects of a measure to be
taken.](https://image.slidesharecdn.com/statisticalqualitycontrolsampling-160806150546/85/Statistical-quality-control-sampling-16-320.jpg)
![(Unit;cm)
№ 1 2 3 4 5 6 7 8 9 10
1 255 259 257 254 253 254 253 257 258 252
2 253 256 255 255 256 255 257 255 256 258
3 257 255 256 251 255 253 255 256 254 256
4 257 255 257 254 254 260 258 253 260 255
5 255 252 255 253 253 258 253 259 255 257
6 253 257 258 256 253 254 255 254 257 253
7 255 254 253 255 257 252 254 256 255 255
8 254 254 254 254 255 255 257 255 253 254
9 258 256 253 256 255 254 255 256 256 256
10 256 254 255 257 254 254 259 253 258 254
Ｓ 253 252 253 251 253 252 253 253 253 252
Ｌ 258 259 258 257 257 260 259 259 260 258
Data sheet of lengths of cut steel wire [Specification: 255±5cm] (n=100)
Histogram--Example No. 1](https://image.slidesharecdn.com/statisticalqualitycontrolsampling-160806150546/85/Statistical-quality-control-sampling-20-320.jpg)
![0
5
10
15
20
25
250 252 254 256 258 260
X
Standard
Lower Limit
Standard
Upper Limit
N=100
[Histogram of Cutting Length of Steel Wire]
Standard Central
=255.19
Products
Standard Value
Histogram--Example No.3](https://image.slidesharecdn.com/statisticalqualitycontrolsampling-160806150546/85/Statistical-quality-control-sampling-22-320.jpg)
![A histogram is mainly used to analyze a process by
examining the location of the mean value in the graph or
degree of variations, to find a problem point that needs to
be improved. Its other applications are listed in the table
below. Usage Results
[Used during phases to monitor the
situation, analyze causes, and review
effectiveness of an action.]
Used to assess the actual conditions.
Used to analyze a process to identify a
problem point that needs to be improved
by finding the location of the mean value
or degree of variations in the graph.
Used to examine that the target quality is
maintained throughout the process.
Can identify the location of the
mean (central) value or degree of
variations.
Can find out the scope of a defect by
inserting standard values.
Can identify the condition of
distribution (e.g., whether there is an
isolated, extreme value).
When is it used and what results will be
obtained?](https://image.slidesharecdn.com/statisticalqualitycontrolsampling-160806150546/85/Statistical-quality-control-sampling-23-320.jpg)
Statistical quality control, sampling
- 10. QC tools (7 QC Tools, New 7 QC Tools) used in solving (or improving) various types of problems that occur in workshops. Whether in identifying causes of problems or in working out their countermeasures, effective use of QC techniques can produce good results quickly and efficiently. It is important to get used to the use of 7 QC Tools. You are encouraged to collect actual data and practice using them. QC tools
- 11. Benefits of using QC tools 1. The situation can be grasped correctly, rather than based on experience or intuition 2. Objective judgment can be made 3. The overall picture can be grasped 4. Problem points and shortcomings become clear so that action can be taken 5. Problems can be shared
- 12. Seven QC Tools Pareto Diagram To identify the current status and issues Cause and Effect Diagram To identify the cause and effect relationship Histogram To see the distribution of data Scatter Diagram To identify the relationship between two things Check Sheet To record data collection Control Chart To find variance and identify the current status Graph / Flow Charts To find variance and identify the current status
- 13. A check sheet is “a sheet designed in advance to allow easy collection and aggregation of data.” By just entering check marks on a check sheet, data can be collected to extract necessary information, or a through inspection can be performed in an efficient manner, eliminating a possibility of skipping any of the required inspection items. A check sheet is also effective in performing stratification (categorization). Check Sheet
- 14. A check sheet used to identify defects Date Vertical Scratch Scratch Dent 6/10 6/126/11 6/13 6/14 Total 34 11 37 Example Usage of Check Sheet Defect
- 15. A Pareto diagram is a combination of bar and line graphs of accumulated data, where data associated with a problem (e.g., a defect found, mechanical failure, or a complaint from a customer) are divided into smaller groups by cause or by phenomenon and sorted, for example, by the number of occurrences or the amount of money involved. (The name “Pareto” came from an Italian mathematician who created the diagram.) Pareto Diagram ０ ４０ ８０ １２０ １６０ （件） ０ ５０ １００ （％） Ａ Ｂ Ｃ Ｄ Ｅ ｎ＝１６０
- 16. When is it used and what results will be obtained? Which is the most serious problem among many problems? It is mainly used to prioritize action. Usage Results •Used to identify a problem. •Used to identify the cause of a problem. •Used to review the effects of an action to be taken. •Used to prioritize actions. [Used during phases to monitor the situation, analyze causes, and review effectiveness of an action.] •Allows clarification of important tasks. •Allows identification of a starting point (which task to start with). •Allows projection of the effects of a measure to be taken.
- 17. A cause and effect diagram is “a fish-bone diagram that presents a systematic representation of the relationship between the effect (result) and affecting factors (causes). Solving a problem in a scientific manner requires clarification of a cause and effect relationship, where the effect (e.g., the result of work) varies according to factors (e.g., facilities and machines used, method of work, workers, and materials and parts used). To obtain a good work result, we must identify the effects of various factors and develop measures to improve the result accordingly. Cause and Effect Diagram
- 18. factors (causes) big bone small bone medium bone mini bone characteristics (result) Name of big bone factor back bone Cause and Effect Diagram
- 19. Yaxis(no.ofoccurrences) specification range range of variation Histogram Articles produced with the same conditions may vary in terms of quality characteristics. A histogram is used to judge whether such variations are normal or abnormal. First, the range of data variations are divided into several sections with a given interval, and the number of data in each section is counted to produce a frequency table. Graphical representation of this table is a histogram. X axis (measured values)
- 20. (Unit;cm) № 1 2 3 4 5 6 7 8 9 10 1 255 259 257 254 253 254 253 257 258 252 2 253 256 255 255 256 255 257 255 256 258 3 257 255 256 251 255 253 255 256 254 256 4 257 255 257 254 254 260 258 253 260 255 5 255 252 255 253 253 258 253 259 255 257 6 253 257 258 256 253 254 255 254 257 253 7 255 254 253 255 257 252 254 256 255 255 8 254 254 254 254 255 255 257 255 253 254 9 258 256 253 256 255 254 255 256 256 256 10 256 254 255 257 254 254 259 253 258 254 Ｓ 253 252 253 251 253 252 253 253 253 252 Ｌ 258 259 258 257 257 260 259 259 260 258 Data sheet of lengths of cut steel wire [Specification: 255±5cm] (n=100) Histogram--Example No. 1
- 21. Histogram--Example No.2 (Frequency Distribution Table Cutting Length of Steel Wire) (Standard: 255±5cm) № Section Central Valee of Each Section Frequency Marking No. of Occurrences 1 250.5-251.5 251 1 2 251.5-252.5 252 3 3 252.5-253.5 253 15 4 253.5-254.5 254 19 5 254.5-255.5 255 24 6 255.5-256.5 256 14 7 256.5-257.5 257 12 8 257.5-258.5 258 7 9 258.5-259.5 259 3 10 259.5-260.5 260 2 100Total
- 22. 0 5 10 15 20 25 250 252 254 256 258 260 X Standard Lower Limit Standard Upper Limit N=100 [Histogram of Cutting Length of Steel Wire] Standard Central =255.19 Products Standard Value Histogram--Example No.3
- 23. A histogram is mainly used to analyze a process by examining the location of the mean value in the graph or degree of variations, to find a problem point that needs to be improved. Its other applications are listed in the table below. Usage Results [Used during phases to monitor the situation, analyze causes, and review effectiveness of an action.] Used to assess the actual conditions. Used to analyze a process to identify a problem point that needs to be improved by finding the location of the mean value or degree of variations in the graph. Used to examine that the target quality is maintained throughout the process. Can identify the location of the mean (central) value or degree of variations. Can find out the scope of a defect by inserting standard values. Can identify the condition of distribution (e.g., whether there is an isolated, extreme value). When is it used and what results will be obtained?
- 24. A scatter diagram is used to “examine the relationship between the two, paired, interrelated data types, ” such as “height and weight of a person.” A scatter diagram provides a means to find whether or not these two data types are interrelated. It is also used to determine how closely they are related to identify a problem point that should be controlled or improved. Number of Rotations Abrasion . .. . . . . . . . . . . . . . . . . .. . . . . . . . . . . .. . . . regression line Scatter Diagram
- 25. Where there is a positive correlation Where there is a negative correlation Where there is no correlation Where there is a non-linear correlation ・ ・・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・・ ・ ・ ・ ・ ・ ・ ・・ ・ ・・ ・ ・ ・ ・ Various Forms of Scatter Diagram The table below shows some examples of scatter diagram’s usage. If, for example, there is a relationship where “an increase in the number of rotations (x) causes an increase in abrasion (y),” there exists “positive correlation.” If, on the other hand, the existence of a relationship where “an increase in the number of rotations (x) causes a decline in abrasion (y)” indicates that there is “negative correlation.” ・
- 26. Control Chart ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● X - R Control Chart Ｘ Ｒ A control chart is used to examine a process to see if it is stable or to maintain the stability of a process. This method is often used to analyze a process. To do so, a chart is created from data collected for a certain period of time, and dots plotted on the chart are examined to see how they are distributed or if they are within the established control limit. After some actions are taken to control and standardize various factors, this method is also used to examine if a process has stabilized by these actions, and if so, to keep the process stabilized.
- 27. ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● × × × × × × × × × × × × × × × × × × × × × × 0 0.5 1.0 5.8 5.4 5.2 0 5 10 15 20 UCL=5.780 CL=5.400 LCL=5.020 N=5 X R Major Application Out of specification: It is necessary to investigate the cause X-R Control Chart
- 28. A graph is “a graphical representation of data, which allows a person to understand the meaning of these data at a glance.” Unprocessed data simply represent a list of numbers, and finding certain tendencies or magnitude of situation from these numbers is difficult, sometimes resulting in an interpretational error. A graph is a effective means to monitor or judge the situation, allowing quick and precise understanding of the current or actual situation. A graph is a visual and summarized representation of data that need to be quickly and precisely conveyed to others. Graph
- 29. When is it used and what results will be obtained? A graph, although it is listed as one of the QC tools, is commonly used in our daily life and is the most familiar means of assessing a situation. Usage Usage Results Used to observe changes in a time-sequential order (line graph) Used to compare size (bar graph) Used to observe Ratios ( pie graph, column graph) A graphs is the most frequently used tool among QC 7 tools. Can recognize changes in a time-sequential order, ratios, and size.