Seven Basic Tools of Quality

SQM -Unit 3 -GRAA SEVEN BASIC TOOLS OF QUALITY Software Quality Management Unit – III Roy Antony Arnold G Asst. Prof. /CSESeven Basic Tools "The Old Seven." "The First Seven." "The Basic Seven." The seven basic tools of quality are first emphasized by Ishikawa, a professor of engineering at Tokyo University. He called father “quality circles”. as of circles . SQM -Unit 3 -GRAAWhy Seven Basic Tools? 􀂅 The Seven Basic Tools of Quality is a designation given to a fixed set of graphical techniques, which are helpful to maintain g p q , p software quality. 􀂅 They are called basic because they are suitable for people with little formal training in statistics and because they can be used to solve the vast majority of quality‐related issues. 􀂅 Good use of the seven basic tools can lead to positive long‐term results for process improvement and quality management in software development. SQM -Unit 3 -GRAAWhat are Seven Basic Tools? 􀂅 The Check List or Check Sheet 􀂅 The Pareto Diagram 􀂅 The Histogram 􀂅 The Diagram Scatter 􀂅 The Run chart (alternately Flow Chart or St tifi ti ) Stratification) 􀂅 The Control Chart 􀂅 The Cause‐and‐Effect Diagram or Ishikawa Diagram or Fish‐Bone Diagram SQM -Unit 3 -GRAAContd... SQM -Unit 3 -GRAACheck List 􀂅 It is a simple document that is used for collecting data in realtiim and at the location where the data is generated. I i i id d ll 􀂅 Its main purpose is to provide a structured way to collect quality‐related data for assessing a process or as an input to other analyses analyses. 􀂅 Bernstein, 1992, observed that the checklists summarize the key points of the process and they are much more effective than the lengthy process documents. 􀂅 Each phase in a software development has a set of tasks to p p complete. Checklists help developers and programmers to ensure that all tasks are complete. SQM -Unit 3 -GRAAContd... 􀂅 Another type of checklist is the common error list, which is part of the stage kickoffs of the defect prevention process (DPP). 􀂅 DPP involves three key steps: 􀂆 (1) analysis of defects to trace the root causes, 􀂆 ( 2) action teams to implement suggested actions, and ) p gg , 􀂆 (3) stage kickoff meetings as the major feedback mechanism 􀂅 PTF ( Program Temporary Fix) is the fix delivered to customers oga e poa y ) s t e de e ed custo e s when they encounter defects in the software system. SQM -Unit 3 -GRAAExample SQM -Unit 3 -GRAAExample 2 SQM -Unit 3 -GRAAPareto Diagram 􀂅 It is a frequency chart of bars in descending order; the frequency bars are usually associated with types of problems. I i d f 19th C I li i d Vilf d 􀂅 It is named after a Century Italian economist named Vilfredo Pareto (1848–1923), who expounded his principle in terms of the distribution of wealth—that a large share of the wealth is owned wealth by a small percentage of the population. 􀂅 In 1950 Juran applied this principle identification to the of quality problems—that most of the quality problems are due to a small percentage of the possible causes. 􀂅 Pareto analysis is commonly referred to as the 80–20 principle (20% of the causes account for 80% of the defects) SQM -Unit 3 -GRAAContd... 􀂅 In software development, the X‐axis is usually the defect cause and the Y‐axis the defect count. I i di hi h bl h ldb l dfi i 􀂅 It indicates which problems should be solved first in eliminating defects and improving the operation. G d dC ll(1986) h P l i f 􀂅 Grady and Caswell (shown a Pareto analysis of software defects by category for four Hewlett‐Packard software projects 􀂅 The top three types (new function or different processing required existing data need to be organized/presented required, differently, and user needs additional data fields) account for more than one‐third of the defects. SQM -Unit 3 -GRAAPareto Analysis for IBM Rochester d product INTF Interface Problems INIT Data Initialization Problems CPLX Complex Logical Problems NLS Translation related National Language Problems g g ADDR Address Problems DEFN Definition Problems SQM -Unit 3 -GRAASQM -Unit 3 -GRAAHistogram It i hi t ti f f t f 􀂅 is a graphic representation of frequency counts of a sample or a population. Th X i li t th it i t l f t ( 􀂅 The X‐axis lists the unit intervals of a parameter e.g., severity level of software defects) ranked in ascending order from left to right and the Y axis contains the right, Y‐frequency counts. The purpose 􀂅 of the histogram is to show the distribution characteristics of a parameter such as overall shape, central tendency dispersion and skewness tendency, dispersion, skewness. 􀂅 It enhances understanding of the parameter of interest. SQM -Unit 3 -GRAASQM -Unit 3 -GRAACustomer Histogram Satisfaction SQM -Unit 3 -GRAAScatter Diagram 􀂅 A scatter diagram vividly portrays the relationship of two interval variables. 􀂅 Compared to tools more other tools, the scatter diagram is difficult to apply. 􀂅 It usually relates to investigative work and requires precise data. It t usua y e ates est gat e o a d equ es p ec se data t is often used with other techniques such as correlation analysis, regression, and statistical modelling. 􀂅 Each point in a scatter diagram represents an observation of both the dependent and independent variables. S tt di idd t b dd i i ki ( if ti i 􀂅 Scatter diagrams aid data‐based decision making e.g., action is planned on the X variable and some effect is expected on the Y variable). SQM -Unit 3 -GRAAContd... 􀂅 One should always look for a scatter diagram when the correlation coefficient of two variables is presented. Th h df l l i h l i ffi i i 􀂅 The method for calculating the correlation coefficient is highly sensitive to outliers, and a scatter diagram can clearly expose any outliers in the relationship relationship. 􀂅 The most common correlation coefficient is Pearson's product moment correlation coefficient, which assumes a linear relationship. 􀂅 If the relationship is nonlinear, the Pearson correlation p , coefficient may show no relationship; therefore, it may convey incorrect or false information. SQM -Unit 3 -GRAACorrelation of Defect Rates of Reused Components B t T Pl tf Between Two PlatformsSQM -Unit 3 -GRAARun Chart 􀂅 A run chart tracks the performance of the parameter of interest over time. 􀂅 These charts serve as real‐time statements of quality as well as workload. 􀂅 The X‐axis is time and the Y‐axis is the value of the parameter. 􀂅 A run chart is best used for trend analysis, especially if data are available for comparisons with historical the current trend. SQM -Unit 3 -GRAAContd... 􀂅 Ishikawa (1989) includes various graphs such as the pie chart, bar graph, compound bar graph, and circle graph under the section that discusses run charts. 􀂅 An example of a run chart in software is the weekly number of open problems in the backlog; it shows the development team's workload of software fixes. SQM -Unit 3 -GRAARun Chart of Percentage of l Delinquent FixesSQM -Unit 3 -GRAAControl Chart Th l h i f l l f hi i 􀂅 The control chart is a powerful tool for achieving statistical process control (SPC). H i f d l i i diffi l 􀂅 However, in software development it is difficult to use control chart in the formal SPC manner. I i f idbl k if i ibl d fi 􀂅 It is a formidable task, not impossible, to define the process capability of a software development process process. 􀂅 A control chart can be regarded as an advanced form of a run for where the process chart situations capability can be defined. SQM -Unit 3 -GRAAContd... 􀂅 It consists of a central line, a pair of control limits (and sometimes a pair of warning limits within the control limits), and values the parameter of interest plotted on the chart of chart, which represent the state of a process. 􀂅 The X‐axis is real time If all values the parameter X time. of are within the control limits and show no particular tendency, the process is regarded as being in a controlled state. 􀂅 If they fall outside the control limits or indicate a trend, the process is considered out of control. Such cases call for causal analysis and corrective actions are to be taken. SQM -Unit 3 -GRAAContd... 􀂅 In statistical terms, process capability is defined: LSL USL C − 􀂅 where USL and LSL are the upper and lower engineering Sigma P 6 = specification limits, respectively, sigma is the standard deviation of the process, and 6 sigma represents the overall i i process variation. 􀂅 If a unilateral specification is affixed to some characteristics, th bilit i d b d fi d ( ) the capability index may be defined: u‐process mean) u USL CP − = LSL u C − = Sigma 3 Sigma P 3 SQM -Unit 3 -GRAAPseudo‐Control Chart of Test Defect Rate—First It ti Iteration SQM -Unit 3 -GRAAExample: 2 SQM -Unit 3 -GRAACause‐and‐Effect Diagram Cause and 􀂅 This was developed by Ishikawa and associates in the early 1950s in Japan. I fi d l i f h ff h d i 􀂅 It was first used to explain factors that affect the production of steel. It sho s the relationship bet een a quality 􀂅 shows between characteristic and factors that affect that characteristic. 􀂅 Its layout resembles a fishbone fishbone. 􀂅 While the scatter diagram describes a specific bivariate relationship in detail cause‐and‐effect diagram identifies detail, the all causal factors of a quality characteristic in one chart. SQM -Unit 3 -GRAACause‐and‐Effect Diagram Cause and Th di h th f t i t 􀂅 These are diagrams show the causes of a certain event 􀂅 Common uses of this diagram are product design and quality defect prevention, to identify potential factors causing an p , y p g overall effect. 􀂅 Causes are usually grouped into major categories to identify these sources variation The categories include: of variation. typically 􀂆 People 􀂆 Methods 􀂆 Machines 􀂆 Materials 􀂆 Measurements 􀂆 Environment SQM -Unit 3 -GRAACause‐and‐Effect Diagram Cause and SQM -Unit 3 -GRAACause‐and‐Effect Diagram Contd. 􀂅 Typical categories causes of are: 􀂆 The 8 Ms (used in manufacturing) 􀂄 Machine (technology) 􀂄 Method (process) 􀂄 Material (Includes Raw Material, Consumables and Information.) 􀂄 Man Power (physical work)/Mind Power (brain work) 􀂄 Measurement (Inspection) 􀂄 Milieu/Mother Nature (Environment) 􀂄 Management/Money Power 􀂄 Maintenance 􀂆 The 8 Ps (used in service industry) 􀂄 Product=Service ▪ Price 􀂄 Place ▪ Promotion/Entertainment 􀂄 People ▪ Process (key person) 􀂄 Physical Evidence ▪ Productivity & Quality 􀂆 The 4 Ss (used in service industry) 􀂄 Surroundings g 􀂄 Suppliers 􀂄 Systems 􀂄 Skills SQM -Unit 3 -GRAA