Explain about the seven basic quality control tools. - MBA Assignment Notes

Explain about the seven basic quality control tools

Answer:
The basic seven control tools considered for achieving quality are Flow Chart, Check sheet, Histogram, Pareto Analysis, Scatter Diagram, Control Chart, and Cause and Effect Diagram for
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, analyzed, 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.
        
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 80-20 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 or3 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 (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

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 + 3. 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.




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.