About Quality Tools

All quality management models (QMS, TQM, etc.) require continuous measurement and improvement of quality. Applied tools, techniques, and methods measure the characteristics of product quality, process, or system while defining actions for improvement.

 Thus, tools and techniques are designed to perform two functions:
-to measure the current performance of the subject of measurement (process, system, product, service, activity, etc.)
-to result in improvement measures by using applied methods.

In quality theory, there are a large number of tools, methods, and techniques for improving quality, and the tools and techniques themselves can be divided into several categories, of which the most logical divisions are:

-statistical methods that apply mathematical statistics in analyzing and interpreting quantitative indicators
-management techniques that require the analysis of qualitative indicators.

Useful questions that we always need to ask ourselves are: why do we need a particular tool? (for ideas, process analysis, cause analysis, planning, evaluation, analysis, etc.), and should we expand or narrow the dimension of observation? and so on.

Next to presented tools: Control charts, Ishikawa (Fishbone) diagram, Histogram, Pareto diagram, Check sheet, Stratification diagram, Gantt chart, FMEA, there are many more as Scatter Diagrams, Flowchart, Check Sheet, Control Plan etc.


Control charts
Control charts are useful for evaluating the stability of a process. They are used to study the variation of the mean, range, and standard deviation for a controlled sample. Each control chart is graphically represented as a diagram. In a very simple way, it is seen when corrective measures are needed and whether there has been an improvement in a certain observed time interval. The use of control charts in monitoring and measuring a process is called Statistical Process Control (SPC). The preparation of control charts is based on statistics and is used either for diagnosing the stability of a process, or for controlling the process, or for confirming that the process is operating under the required conditions. Control charts are good for early detection of errors.


Ishikawa diagram (Fishbone diagram)
The Ishikawa diagram (Fishbone diagram) is also known as a cause-and-effect diagram because it graphically shows the relationship between cause and effect in an extremely simple way. Kaoru Ishikawa, a Japanese quality guru, developed these diagrams in the 1950s. It is used for systematically investigating all possible causes that make up an occurrence (process, activity, error). The result of a process is influenced by a multitude of factors between which causal relationships are not immediately visible. This diagram provides a good basis for a complete analysis of the causes and effects of a phenomenon (error, problem).


A histogram is a tool that displays the distribution of errors, occurrences, and/or activities in graphic form and is very easy to understand. The histogram shows data according to their frequencies of occurrence. Each column represents one tested error (occurrence, activity). The height of the column is the frequency of occurrence. The histogram is good because it shows all values (including extremes), provides graphic (visual) information about a process (phenomenon, activity), and helps to make decisions about possible improvement opportunities.


Pareto diagram
A Pareto diagram is used when it is necessary to identify the relative importance of different details of a process (or group of errors) from a large number of different facts in some way. This diagram is used to identify the most important problems, discover the causes of problems, etc. The Pareto diagram usually confirms the “80-20” rule, which states that 80% of errors (problems) are caused by 20% of factors (causes). In practice, of course, the 80-20 rule does not always have to be absolutely valid, but approximately this ratio (75-25, 70-30, etc.).


Check sheet
Also called: defect concentration diagram, is used when it is necessary to collect errors or occurrences in a simple and clear way. This way, all types of errors and their frequency are displayed in a table format because the tabular form is suitable for further analysis. From the tables, trends can be established based on which further exploitation of results and specific corrective measures can be approached.


Stratification diagram
Stratification is a technique used in combination with other data analysis tools. When data from different sources or categories are merged, the meaning of the data can become invisible. This technique helps to separate the data so that patterns can be seen, i.e. it allows multiple subsets to be presented on one diagram.
When to use a stratification diagram
-Before collecting data
-When data comes from multiple sources, such as shifts, days of the week, suppliers, or population groups
-When data analysis requires the separation of different data sources


Gantt chart
A Gantt chart is a type of bar chart that illustrates a project schedule. The Gantt chart illustrates the start and end dates of individual project elements as well as their overview. Some Gantt charts also show the dependence (i.e. precedence network) relationships between activities. Gantt charts can be used to display the current schedule of the chart.


The FMEA method involves classifying potential failures based on their severity, frequency, and detection capacity.

To start the FMEA technique, the initial step is to create a list of possible failures that could occur within a system or process. It is essential to have a multidisciplinary group with extensive experience in the particular process or system being analyzed to ensure that all possible failures are considered. Once the failures have been identified, their effects on the system are analyzed, and a severity level is assigned to each one based on a scale of 1 to 10. The next step involves identifying the causes of each failure and assessing their level of occurrence, also quantified on a scale of 1 to 10. The controls that are currently in place to prevent the failures are listed, and their detection capacity is quantified on the same scale of 1 to 10. Finally, the severity, occurrence, and detection capacity scores are multiplied, providing a value that ranks each failure in order of importance. The highest-ranked failures are given priority for corrective actions. Once the FMEA is completed, recommended actions are taken to reduce the values of the most relevant failures detected.

It is important to note that the FMEA is a snapshot of a specific moment and time. As corrective actions are carried out, the document should be reviewed and updated accordingly. It is a living quality document that requires frequent updating to remain effective.



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