CHAPTER 5: QUALITY TOOLS AND SIX SIGMA METRICS

When to use a Pareto charts ?

1. When analyzing data about the frequency of problems or causes in a process 2. When there are many problems or causes and you want to focus on the most significant 3. When analyzing broad causes by looking at their specific components 4. When communicating with others about your data

When to use the fishbone diagram ?

1. When identifying possible causes for a problem 2. When a team's thinking tends to fall into ruts

The basic procedure for creating a flowchart 1. Define the process to be diagrammed. Write it at the top of the work surface. Discuss and decide on the boundaries of your process: Where or when does the process start? Where or when does it end? Discuss and decide on the level of detail to be included in the diagram.

2. Brainstorm the activities that take place. Write each on a card or sticky note. Sequence is not important at this point, although thinking in sequence may help people remember all the steps. 3. Arrange the activities in proper sequence.

How to create a Pareto chart? 1. Decide what categories you will use to group items. 2. Decide what measurement is appropriate. Common measurements are frequency, quantity, cost, or time.

3. Decide what period of time the chart will include. 4. Collect the data, recording the category each time. Or assemble data that already exists. 5. Subtotal the measurements for each category. 6. Determine the appropriate scale for the measurements you have collected. The maximum value will be the largest subtotal from step 5. If you will do optional steps 8 and 9, the maximum value will be the sum of all subtotals from step 5. Mark the scale on the left side of the chart.

Procedures on how to create a scatter diagram! (Part1) 1. Collect pairs of data where a relationship is suspected. 2. Draw a graph with the independent variable on the horizontal axis and the dependent variable on the vertical axis. For each pair of data, put a dot or a symbol where the x-axis value intersects the y-axis value. If two dots fall together, put them side by side, touching, so that you can see both.

3. Look at the pattern of points to see if a relationship is obvious. If the data clearly form a line or curve, you may stop. The variables are correlated. You may wish to use regression or correlation analysis now. Otherwise move to step 4 through 7

The basic procedures for creating a run chart 1. Decide on the vertical scale, based on the range of measurements you expect to see. Decide on the horizontal time scale, based on the frequency of measurements. Mark and label the scales. 2. If you already have some data, calculate the average:

3. Plot each measurement in the time order it occurs. Connect points with straight lines.

When to use a check sheet ? 1. When data can be observed and collected repeatedly by the same person or at the same location, and ... 2. When collecting data on the the frequency or patterns of events, problems. defects location, defect causes, and so forth, or . ..

3. When collecting data from a production process

When to use a scatter diagram ? 1. When you have paired numerical data, and 2. When the dependent variable may have multiple values for each value of the independent variable, and

3. When trying to determine whether the two variables are related, such as When trying to identify potential root causes of problems, or... After brainstorming causes and effects using a fishbone diagram, to determine objectively whether a particular cause and effect are related, or.. When determining whether two effects that appear to be related both occur with the same cause, or. . . When testing for autocorrelation before constructing a control chart

Procedures for creating a check sheet 1. Decide what event or problem will be observed. Develop operational definitions. 2. Decide when data will be collected and for how long. 3. Design the form. Set it up that data can be recorded simply by making check marks or Xs or similar symbols and so that data does not have to be recopied for analysis.

4. Label all spaces of the form 5. Test the check sheet for a short trial period to be sure it collects the correct data and is easy to use. 6. Each time the targeted event or problem occurs, record data on check sheet

When to use histogram ? 1. When the data are numerical, and . . . 2. When you want to see the shape of the data's distribution, especially 3. When determining whether the output of a process is distributed normally..

4. When analyzing whether a process can meet the customer's requirements 5. When analyzing what the output from a suppliers process looks like 6. When seeing whether a process change has occurred from one time period to another 7. When determining whether the outputs of two or more processes are different 8. When you wish to communicate the distribution of data quickly and easily to others

Procedures on how to create scatter diagram (Part2) 4. Divide points on the graph into 4 quadrants. If there are X points on the graph. -Count X/2 point s from top to bottom and draw a horizontal line. -Count X/2 points from left to right and draw a vertical line. If the number of points is odd, draw the line through the middle points.

5. Count the points in each quadrant. Do not count points on a line.

The basic procedure for creating a flowchart 4. When all activities are included and everyone agrees that the sequence is correct, draw arrows to show the flow of the process.

5. Review the flowchart with others involved in the process (workers, supervisors, suppliers, customers) to see if they agree that the process is as drawn.

Procedure on how to create scatter diagram (Part3) 6. Add the diagonally opposite quadrants. Find the smaller sum and the total of points in all quadrants. A= points in upper left + points in lower right B= points in upper right + points in lower left Q= the smaller of A and B N= A + B

7. Look up the limit for N on the trend test table. -If Q is less than the limit, the two variables are related -If Q is greater than or equal to the limit, the pattern could have occurred from random chance

Trend.

A series of points heading up or down. If the chart has 20 to 100 points, there should be no more than six in a row steadily increasing or decreasing. For fewer than 20 points, the limit is five. Or use the method described for the scatter diagram to decide if the number of points indicates a trend.

This diagram is used as a next step to document the final list of causes from the brainstorming session. The participants in the session should include people with a working knowledge of the process as well as those with a theoretical background.

Cause and effect Diagrams

Is an alternative approach employed by some organizations where the fishbone diagram is displayed on a huge wall or board and employees are encouraged to identify causes by writing on it or using sticky notes.

Cause and effect diagram with the addition of cards. (CEDAC)

This simple tool provides a method of easy data collection. By collection data on a _______, common patterns or trends can be identified.

Check sheet

Steps that aid the development of a flowchart are as follows: 7. Communicate the flowchart to all stakeholders

Communicate the flowchart to all stakeholders

Steps that aid the development of a flowchart are as follows: 6. Identify opportunities for removal of redundancies, waste reduction, simplification, and standardization

Identify opportunities for removal of redundancies, waste reduction, simplification, and standardization

3 patterns to look for in a run chart to analyze the data. These are also known as statistical test.

Length of Run Number of Runs Trend

Scatter diagram :Negative correlation

Negative correlation

Scatter diagram :No correlation

No correlation

A Pareto chart is a bar graph. The lengths of the bars represent frequency or cost (time or money) and are arranged with the longest bars on the left and the shortest to the right. In this way, the chart visually depicts which situations are more significant. This cause analysis tool is considered one of the seven basic quality tools.

Pareto Charts

A ______is a bar graph. The length of the bars represents frequency or cost (money or time), and they are arranged in order from longest on the left to shortest on the right. Therefore, the chart visually shows which situations are more significant.

Pareto chart

Scatter diagram :Positive correlation

Positive correlation

Number of Runs.

The average line is crossed too few or too many times. Use the number of runs table (Table 5.17) for this test. Count the total number of points, skipping any points lying directly on the averageline. Determine the number of runs by counting the number of times the line between data points crosses the average line. If the data line touches the average line and then returns to the same side, do not count it as crossing.

A thorough understanding of process inputs and outputs and their relationships is a key step in process improvement. The_________(also called the Ishikawa diagram or fishbone diagram) traditionally divides causes into several generic categories.

The cause and effect diagram

A process is often diagrammed with a flowchart depicting: 1. Inputs 2. Outputs 3.

The path that material or information follows

Length of Run

Too many consecutive points on one side of the average.

Do not assign a "technical expert" to draw the flowchart. People who actually perform the process should construct the flowchart. True or False.

True

Elements that may be included in a flowchart are a sequence of actions, materials or services entering or leaving the process (inputs and outputs), decisions that must be made, people who become involved, time involved at each step, and/or process measurements. True or False.

True

If the scatter diagram shows no relationship between variables, consider whether the data might be stratified. True or False.

True

Keep all parts of the flowchart visible to everyone all the time. That is why flipchart or newsprint should be used rather than transparencies or a whiteboard. True or False.

True

Run charts are best for spotting runs of data points lying on one side of the centerline or a sequence of points headed in one direction.True or False.

True

Several sessions may be necessary. This allows members time to gather information or to reflect on the process. Even if the flowchart seems to be finished in one session, plan a review at a second session, to allow reflection time. True or False.

True

True or False. Even if a scatter diagram shows a relationship, do not assume that one variable caused the other. Both may be influenced by a third variable.

True

The facilitator's role is to be sure all members participate, to ask the right questions to uncover all aspects of the process, and to help team members capture all their ideas in the language of the flowchart. True or False.

True.

The histogram is helpful for comparing "before and after" improvement readily while waiting for a more detailed analysis. True or False.

True.

These tests for patterns are based on statistics. They test whether the data are truly statistically random. If not, an underlying pattern needs to be identified. True or False.

True. (run chart)

True or False. The run chart is used to identify patterns in process data.

True. A run chart is typically used when the subgroup size is one. When the subgroup size is greater than one, the subgroup means or medians are calculated and connected with a line, similar to a control chart.

Check sheets are used to observe or review a process. True or False.

True. Check sheets are usually used during the execution of the process.

True or False. Check sheets can be the basis for other analytical tools and are incorporated into attribute process behavior charts.

True. Creating and using a check sheet helps keep a focus on continual improvement, and the may foster changes.

The scatter diagram is created with the independent variable as the "X" axis and the dependent variable as the "Y" axis. If one is cause and the other is effect, then effect is the dependent variable and cause is the independent variable. True or False.

True. Data is obtained in pairs (X,Y) and once the data pairs are plotted for the range of the axis, the plotted data can be interpreted.

Run charts do not judge whether patterns are desirable or undesirable. True or False.

True. For example, a trend may be toward better performance or toward worse performance. It is just as important to do something to understand and maintain good performance as it is to eliminate bad performance.

If a line is not clear, statistics (N and Q) determines whether there is reasonable certainly that a relationship exists. True or False.

True. If the statistics say that no relationship exists, the pattern could have occurred by random chance.

Identify and involve in the flowcharting process all key people who are involved with the process. This includes those who do the work in the process: suppliers, customers, and supervisors. True or False.

True. Involve them in the actual flowcharting sessions by interviewing them before the sessions and/or by showing them the developing flowchart between work sessions and obtaining their feedback.

True or False. Run charts do not have statistical control limits to monitor variation.

True. Run charts are related to statistical tests that can be performed to detect trends, oscillation, mixtures, and clustering.

Drawing a scatter diagram is the first in looking for a relationship between variables. True or False.

True. See correlation analysis and regression analysis for statistical methods you can use.

Computer software is available for drawing flowcharts. True or False.

True. Software is useful for drawing a neat final diagram, but the method given here works better for the messy initial stages of creating the flowchart.

If the diagram shows no relation, consider whether the independent (x-axis) variable has been varied widely. True or False.

True. Sometimes a relationship is not apparent because the data dont cover a wide enough range.

Run charts are not as powerful as control charts for analyzing process data and identifying problems. True or False. However, run charts provide a quick preliminary check for obvious problems and also are useful if you don't have enough data yet for a control chart.

True. The out-of-control tests used for control charts cannot be used with run charts because there are no control limits and no calculation of sigma.

Don't worry too much about drawing the flowchart the "right way." True or False.

True. The right way is the way that helps those involved understand the proces

What kind of situation might you use a scatter diagram ? (Part2)

Variable A is the number of employees trained on new software, and variable B is the number of calls to the computer help line. You suspect that more training reduces the number of calls. Plot number of people trained versus number of calls.

What kind of situation might you use a scatter diagram ?

Variable A is the temperature of a reaction after 15 minutes. Variable B measures the color of the product. You suspect higher temperature makes the product darker. Plot temperature and color on a scatter diagram.

Steps that aid the development of a flowchart are as follows: 5. Walk through the process to test the flowchart

Walk through the process to test the flowchart

1. To develop an understanding of how a process is done 2. To study a process for improvement 3. To communicate to others how a process is done 4. When better communication is needed between people involved with the same process 5. To document a process 6. When planning a project

When to use a flowchart ?

When to use a run chart When monitoring a continuous variable over time, and . . . When looking for patterns, such as cycles, trends, or changes in the average, and . . .

When you want a quick preliminary analysis to find obvious problems, before the effort of constructing control charts, or . . . When insufficient points have been collected to draw a control chart yet

Steps that aid the development of a flowchart are as follows: 2. Write down the steps in the process

Write down the steps in the process

This cause analysis tool is considered one of the seven basic quality tools. The________ diagram identifies many possible causes for an effect or problem. It can be used to structure a brainstorming session. It immediately sorts ideas into useful categories.

fishbone

A ______ is a picture of the separate steps of a process in sequential order. Elements that may be included are a sequence of actions, materials, or services entering or leaving the process (inputs and outputs), decisions that must be made, people who become involved, time involved at each step, and/or process measurements. The process described can be anything: a manufacturing process, an administrative or service process, or a project plan. Usually listed as one of the seven QC tools, this is a generic tool that can be adapted for a wide variety of purposes.

flowchart

A ___________ distribution shows how often each different value in a set of data occurs.

frequency

A Run chart test can detect trends, oscillation, mixtures, and clustering. These are _______ patterns and suggest that the variation observed can be attributed to _______. Lack of steadiness in a process can cause oscillation. A trend can be either upward or downward due to, for example, tool wear or loosening of a fixture in a piece of equipment.

nonrandom; special causes

The ______ graph and _______ polygon graph show how many measurements (or what percentage of measurements) are less than or equal to each value.

percentile graph; cumulative polygon graph

The ______ graph shows each data point as a small circle along a vertical line.

point graph

The _______ chart takes the shape of a histogram buts connects the frequency values by using with a line instead of showing bars.

polygon

Understanding and improving a ______ is a key part of every Six Sigma project.

processes

The _______ and _____ display preserves individual values by using them as symbols for the data point.

stem and leaf

When to use a flowchart To develop an understanding of how a process is done, or . . . To study a process for improvement, or . . . To communicate to others how a process is done, or . . .

• To document a process, or • When planning a project When better communication is needed between people involved with the same process, or . . .

Is a picture of the separate steps of a process in sequential order. It is a generic tool that can be adapted for a wide variety of purposes, and can be used to describe various processes, such as a manufacturing process, an administrative or service process, or a project plan. It's a common process analysis tool and one of the seven basic quality tools.

Flowchart

Is a quality tool (and a business process tool) that helps individuals visualize a process in discrete steps arranged in the sequence of events

Flowchart

The success of utilizing a Cause and Effect Diagram with Cards depends on a company ________ and _______.

culture; communication.

How to create a Pareto chart? 7. Construct and label bars for each category. Place the tallest at far left, then the next tallest, and so on. If there are many categories with small measurements, they can be grouped as "other."

8. Calculate the percentage for each category: the subtotal for that category divided by the total for all categories. Draw a right vertical axis and label it with percentages. Be sure the two scales match. For example, the left measure- ment that corresponds to one-half should be exactly opposite 50 percent on the right scale. 9. Calculate and draw cumulative sums: Add the subtotals for the first and second categories, and place a dot above the second bar indicating that sum. To that sum add the subtotal for the third category, and place a dot above the third bar for that new sum. Continue the process for all the bars. Connect the dots, starting at the top of the first bar. The last dot should reach 100 percent on the right scale.

A structured, prepared form for collecting and analyzing data. This is a generic tool that can be adapted for a wide variety of purposes.

A check sheet

Is an easy to use tool for graphically summarizing continuous data collected from a process. The frequency of data occurrence is reflected as bars of various heights and data is grouped by intervals. Shows the shape of the data, centering of the process, variation, and a rough distribution of the data.

A histogram

Is the most commonly used graph to show frequency distributions. It looks very much like a bar chart, but there are important differences between them.

A histogram

Is a series of steps for producing products and/or services.

A process

All of the individual observations are plotted in a time sequence, and a horizontal reference line is drawn at the median. This is called ______.

A run chart

Is a line graph showing a process measurement on the vertical axis and time on the horizontal axis. Often, a reference line shows the average of the data. Reveals patterns in the data over time. Unlike a control chart, it does not show control limits.

A run chart

Graphs pairs of numerical data, one variable on each axis, to look for a relationship between them. If the variables are corelated, the points will fall along a line or curve. The better the correlation, the tighter the points will hug the line.

A scatter diagram

Is used to explore the relationship between two sets of variables. This diagram provides a visual display of correlation between the variables. This tool should be used in conjunction with the cause and effect diagram.

A scatter diagram

Steps that aid the development of a flowchart are as follows: 1. Determine the scope of the flowchart with boundaries

Determine the scope of the flowchart with boundaries

Steps that aid the development of a flowchart are as follows: 4. Draw the flowchart (use appropriate flowcharting symbols for ease of understanding)

Draw the flowchart

Scatter diagram :Quadratic relationship

Quadratic relationship

Steps that aid the development of a flowchart are as follows: 3. Rearrange if required to reflect the current sequence of steps

Rearrange where required to reflect the current sequence of steps