When discussing the quality control tools, there are seven types of tools that are being used in the business organizations in order to have quality improvements.These tools can be categorized as follows.
Seven Quality control tools
Pareto chart is a bar graph. These charts depict the situations that are most significant. Further, these bar graphs can be useful in various situations like,
• In analyzing the data according to the frequency of problems or causes in a process.
• In focusing on the most significant problems or causes.
• Analyzing broad causes by looking at the specific components.
• Communicating with others regarding the data.
Fishbone diagram can also be called as Ishikawa diagram, It identifies many possible causes for an effect or problem and also it can be useful to structure a brainstorming session. It sorts out ideas into useful categories.
Stratification is a technique used in combination with the other data analysis tools. This technique separates the data so that the patterns can be seen. Stratification is used,
• Before collecting the data.
• When data is generated from a variety of sources such as shifts, days of the week, suppliers or population groups.
• When the data analysis may require separating different sources or conditions.
A check sheet, also know as defect concentration diagram, is a structured, prepared form of collecting and analyzing data. This is a generic tool that can be adapted for a different kind of purposes. Check sheets are used,
• When the data can be observed and collected repeatedly by the same person or at the same location.
• When collecting data on the frequency or patterns of events, problems, defects, defect locations, defect causes, etc.
• When collecting data from a production process.
A histogram is the most commonly used graph to indicate frequency distributions. It shows the frequency of each different values in a set of data. It is almost similar to a bar chart. Histograms are used,
• When the data is numerical.
• When it is required to see the shape of the data’s distribution. Histograms are especially used when determining whether the output of a process is distributed approximately normally.
• When analyzing whether a process can meet up the customer requirements.
• When analyzing the output from a supplier’s process.
• To check whether the process changes occurred from one-time period to another.
• To check the differences of the outcomes of two or more processes.
• To communicate the data distribution quickly and easily to others.
The scatter diagram graphs the pairs of numerical data with one variable on each axis to consider the relationship between them. If the variables are correlated, the points fall along a line or a curve. Scatter diagrams are also known as scatter plot or X-Y graph.
Scatter diagrams are used,
• To pair the numerical data.
• When the dependent variable may have multiple values with each of the independent variable.
• When trying to identify the potential root causes for the problems.
• To identify the relationship between two variables.
A control chart is a graph used to study the process changes over time. Data is plotted in time order. A control chart always has a central line for the average, a lower line for the lower control limit and an upper line for the upper control limit . These lines are determined from the historical data. By comparing current data to these lines, conclusions are made regarding the process variations.Control charts are used in,
• Controlling the ongoing processes by finding and correcting the problems as they occur.
• Predicting the expected range of outcomes from a process.
• Determining whether a process is stable in the statistical control.
• Analyzing the patterns of process variations from special causes or common causes.