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MB0044 Q4. Explain the different types of Quality Control Tools with examples? How do Crosby’s absolutes of quality differ from Deming’s principles?

Answer: Quality Control Tools
Flow Chart, Check sheet, Histogram, Pareto Analysis, Scatter Diagram, Control Chart, and Cause and Effect Diagram are the basic seven control tools considered for achieving quality.
Quality Control Tools

a) Flow Chart: Flow chart is a visual representation of process showing the various steps. It helps in locating the points at which a problem exists or an improvement is possible. Detailed data can be collected, analysed, and methods for correction can be developed using flow charts. The various steps include:

• Listing out the various steps or activities in a particular job

• Classifying them as a procedure or a decision
Each decision point generates alternatives. Criteria and consequences that go with decisions are amenable to evaluation for purposes of assessing quality. The flow chart helps in pin-pointing the exact points at which errors have crept in.
Sample flow chart
b) Check Sheet: Check sheets are used to record the number of defects, types of defects, locations at which they are occurring, times at which they are occurring, and workmen by whom they are occurring. The sheet keeps a record of the frequencies of occurrence with reference to possible defect causing parameters. It helps to implement a corrective procedure at the point where the frequencies are more.

The table shows that the number of defects 1 and 5 are not many as compared to defect no 2 which increased over the days and appears to be stabilising at the higher side and therefore needs to be attended immediately. The column which shows days can be changed to observed by the hour, if need be.

c) Histogram – Histograms are graphical representations of distribution of data. They are generally used to record huge volumes of data about a process. They reveal whether the pattern of distribution has a single peak, or many peaks and also the extent of variation around the peak value. This helps in identifying whether the problem is serious. When used in conjunction with comparable parameters, the visual patterns help us to identify the problem which should be attended to.
Sample histogram chart

The values shown are the number of observations made regarding a parameter. Sometimes, the percentages are shown to demonstrate the relative contribution of each of the parameters.

d) Pareto Analysis: Pareto analysis is a tool for classifying problem areas according to the degree of importance and attending to the most important. Pareto principle, also called 8020 rule, states that 80 percent of the problems that we encounter arise out of 20 percent of items. If we find that, in a day, we have 184 assemblies having problems and there are 11 possible causes, it is observed that 80 percent of them, that is, 147 of them have been caused by just 2 or 3 of them. It will be easy to focus on these 2 or 3 and reduce the number of defects to a great extent. When the cause of these defects has been attended, we will observe that some other defect becomes predominantly observed and if the process is continued, we are marching toward zero defects.

e) Scatter Diagram: Scatter diagram is used when we have two variables and want to know the degree of relationship between them (See Figure 6.5 for Sample scatter diagram). We can determine if there is cause and effect relationship between the variables and the degree of extent over a range of values of the variables. Sometimes, we can observe that there is no relationship, in which we can change one parameter being sure that it has no effect on the other parameter.

Sample scatter diagram

f) Control Charts: Control charts are used to verify whether a process is under control. Variables, when they remain within a range, will render the product and maintain the specifications. This is called the quality of conformance. The range of permitted deviations is determined by design parameters. Samples are taken and the mean and range of the variable of each sample (subgroup) is recorded. The mean of the means of the samples gives the control lines. Assuming normal distribution, we expect 99.97 percent of all values to lie within the Upper Control Limit (UCL) and Lower Control Limit (LCL) – corresponding to

+ 3σ. The graphical representation of data helps in changing settings to bring back the process closer to the target.

g) Cause and Effect Diagram: Cause and effect diagram represents all the possible causes which lead to a defect on quality characteristics. These are arranged in such a way that different branches representing causes connect the stem in the direction of the discovery of the problem (See Figure 6.6 for Sample cause and effect diagram). When each of them is investigated thoroughly we will be able to pin-point some factors which cause the problem. We will also observe that a few of them can have cumulative effect or even a cascading effect.

When we observe that we have excessive defects from a machine, we try to identify all possible sources of the causes of defects. We make a study of each of them and try to correct it.

Deming Principle

Deming's TQM helps organisations to improve the quality of the products and services they offer. Deming’s approach is summarised in his 14 points.

1. Constancy of purpose for continuous improvement

2. Adopt the TQM philosophy for economic purposes

3. Do not depend on inspection to deliver quality

4. Do not award any business based on price alone

5. Improve the system of production and service constantly

6. Conduct meaningful training on the job

7. Adopt modern methods of supervision and leadership

8. Remove fear from the minds of everyone connected with the organisation

9. Remove barriers between departments and people

10. Do not exhort, repeat slogans, and put up posters

11. Do not set-up numerical quotas and work standards

12. Give pride of workmanship to the workmen

13. Education and training to be given vigorously

14. State and exhibit top management’s commitment for quality and productivity

Using the above principles, Deming gave a four step approach to ensure a purposeful journey of TQM . The slope is shown to indicate that if efforts are let up the programme will roll back.

• Plan means that a problem is identified, processes are determined and relevant theories are checked out.

• Do means that the plan is implemented on a trial basis. All inputs are correctly measured and recorded.

• Check means that the trials taken according to the plan are in accordance with the expected results.

• Act means when all the above steps are satisfactory regular production is started so that quality outcomes are assured.

Crosby’s absolutes of quality

Like Deming, Crosby also lays emphasis on top management commitment and responsibility for designing the system so that defects are not inevitable. He urged that there be no restriction on spending for achieving quality. In the long run, maintaining quality is more economical than compromising on its achievement. His absolutes can be listed as under:

• Quality is conformance to requirements, not ‘goodness’

• Prevention, not appraisal, is the path to quality

• Quality is measured as the price paid for non-conformance and as indices

• Quality originates in all factions. There are no quality problems. It is the people, designs, and processes that create problems

Crosby also has given 14 points similar to those of Deming. His approach emphasises on measurement of quality, increasing awareness, corrective action, error cause removal and continuously reinforcing the system, so that advantages derived are not lost over time. He opined that the quality management regimen should improve the overall health of the organisation and prescribed a vaccine. The ingredients are:

1) Integrity: Honesty and commitment help in producing everything right first time, every time

2) Communication: Flow of information between departments, suppliers, customers helps in identifying opportunities

3) Systems and operations: These should bring in a quality environment so that nobody is comfortable with anythin

1 comment:

  1. Out of 2000 people surveyed, 1200 belong to urban areas and rest to semi urban areas. Among 1000 who visited other regions, 800 belonged to urban areas. Test at 5% level of significance whether area and visiting other states is dependant.


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