Quality tools help people understand and improve processes. There is different variety of tools, and the skill of quality professionals lies in their ability to take an application from one field or industry and apply it, or adapt it, to specific situations in other fields.
Basic Healthcare Quality Tools
The seven tools are:
- Check sheet
- Control chart
- Stratification (alternately, flow chart or run chart)
- Pareto chart
- Cause and effect diagram (also known as the “fishbone” or Ishikawa diagram)
- Scatter diagram
A check sheet is a form or the document used to collect data in real time at the location where the data is generated. The data that it captures can be quantitative or qualitative. When the information is quantitative the check sheet is called a tally sheet.
When to Use a Checksheet
- When data can be observed and can be collected repeatedly by the same person or at the same location.
- When collecting data on the frequency or patterns of events, problems, defects, defect location, defect causes, or similar issues.
- When collecting data from a production process.
Check Sheet Procedure
- Decide what events or problems will be observed. Develop operational definitions.
- Decide when the data will be collected and for how long.
- Design the form. Set it up so that the data can be recorded simply by making check marks or X’s or similar symbols and so that data do not have to be recopied for analysis.
- Label all spaces on the form.
- Test the check sheet for the short trial period to be sure it collects the appropriate data and is easy to use.
- Each time a targeted event or problem occurs, record data on the check sheet.
The control chart is a graph used to study how a process changes over time. Data are plotted in time order. A control chart always has the central line for the average, an upper line for the upper control limit and the lower line for the lower control limit. These lines are determined from historical data. By comparing the current data to these lines, you can draw conclusions about whether the process variation is consistent (in control) or is unpredictable (out of control, affected by special causes of variation). This versatile data collection and the analysis tool can be used by a variety of industries and is considered one of the seven basic quality tools.
Control charts for the variable data are used in pairs. The top chart monitors the average or the centering of the distribution of data from the process. The bottom chart monitors the range or the width of distribution. If your data were shots in the target practice, the average is where the shots are clustering, and the range is how tightly they are clustered. Control charts for attribute data are used singly.
When to Use a Control Chart
- When controlling the ongoing processes by finding and correcting problems as they occur.
- When predicting an expected range of outcomes from a process.
- When determining whether the process is stable (in statistical control).
- When analyzing the patterns of process variation from special causes (non-routine events) or common causes (built into the process).
- When determining whether your quality improvement project should aim to prevent specific problems or to make fundamental changes in the process.
Control Chart Basic Procedure
- Choose the appropriate control chart for the data.
- Determine the appropriate time period for collecting and plotting the data.
- Collect data, construct your chart and analyze the data.
- Look for “out-of-control signals” on the control chart. When one is identified mark it on the chart and investigate the cause. Document how you has investigated, what you learned, the cause and how it was corrected.
Flow Chart/Run Chart
Also called: process flowchart, process flow diagram.
Variations: macro flowchart, top-down flowchart, a detailed flowchart (also called process map, micro map, service map or the symbolic flowchart), deployment flowchart (also called down-across or cross-functional flowchart), several-leveled flowchart.
A flowchart is a picture of separate steps of a process in sequential order. It is the common process analysis tool and one of the seven basic quality tools.
Elements that may be included in the flowchart are a sequence of actions, materials or services entering or leaving the process (inputs and outputs), decisions that must be made, the people who become involved, time involved at each step and/or process measurements.
A flowchart is a generic tool that can be adapted for a wide variety of purposes, and can be used to describe various processes, such as the manufacturing process, an administrative or service process, or a project plan.
When to Use a Flow Chart
- To develop an understanding of how a process is done.
- To study the process for improvement.
- To communicate to others how the process is done.
- When better communication is needed between people involved with the same process.
- To document a process.
- When planning a project.
Flow Chart Basic Procedure
- Materials needed: sticky notes or the cards, a large piece of flipchart paper or newsprint, marking pens.
- Define the process to be diagrammed. Write its title at the top of work surface.
- Discuss and decide on the boundaries of the process: Where or when does the process start? Where or when does it end? Discuss and decide on the level of details to be included in the diagram.
- Brainstorm the activities that take place. Write each on a card or sticky note.
- Arrange the activities in proper sequence.
- When all the activities are included and everyone agrees that the sequence is correct, draw arrows to show the flow of the process.
- Review the flowchart with the others involved in the process (workers, supervisors, suppliers, customers) to see if they agree that the process is drawn accurately.
Also called: Pareto diagram, Pareto analysis
Variations: weighted Pareto chart, comparative Pareto charts
A Pareto chart is a bar graph. The lengths of the bars represent the frequency or cost (time or money) and are arranged with longest bars on the left and the shortest to the right. In this way the chart visually depicts that which situations are more significant. This is the cause analysis tool is considered one of the seven basic quality tools.
When to Use a Pareto Chart
- When analyzing the data about the frequency of problems or causes in a process.
- When there are many problems or causes and you want to focus on the most significant one.
- When analyzing the broad causes by looking at their specific components.
- When communicating with others about the data.
Pareto Chart Procedure
- Decide what categories you will use to group the items.
- Decide what measurement is appropriate. Common measurements are frequency, quantity, cost and time.
- Decide that what period of time the Pareto chart will cover: One work cycle? One full day? A week?
- Collect the data, recording the category each time, or assemble data that already exist.
- Subtotal the measurements for each category.
- 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 the optional steps 8 and 9 below, the maximum value will be the sum of all subtotals from step 5.) Mark the scale on the left side of the chart.
- Construct and label bars for each category. Place the tallest at far left, then the next tallest to its right and so on. If there are many categories with the small measurements, they can be grouped as “other.”
- Note: Steps 8 and 9 are optional but are useful for the analysis and communication.
- Calculate the percentage for every category: the subtotal for that category divided by the total for all categories. Draw the right vertical axis and label it with percentages. Be sure that the two scales match: For example, the left measurement that corresponds to one-half should be exactly opposite 50% on the right scale.
- 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 percentages on the right scale.
A frequency distribution shows how often each different value in a set of data occurs. A histogram is the most commonly used graph to show frequency distributions. It looks very much like the bar chart, but there are important differences between them.
When to Use a Histogram
Use a histogram when:
- The data are numerical.
- You want to see the shape of the data distribution, especially when determining whether the output of a process is distributed approximately normally.
- Analyzing whether the process can meet the customer’s requirements.
- Analyzing what is the output from a supplier’s process looks like.
- Seeing whether the process change has occurred from one time period to another.
- Determining whether the outputs of two or more processes are different.
- You wish to communicate distribution of data quickly and easily to others.
How to create a Histogram
- Collect at least 50 consecutive data points from the process.
- Use a histogram worksheet to set up the histogram. It will help you to determine the number of bars, the range of numbers that go into each bar and the labels for the bar edges. After calculating W in Step 2 of the worksheet, use your judgment to adjust it to a convenient number. For example, you might decide to round 0.9 to an even 1.0. The value for W must not have more decimal places than the numbers you will be graphing.
- Draw x- and y-axes on graph paper. Mark and label the y-axis for counting data values. Mark and label the x-axis with the L values from the worksheet. The spaces between these numbers will be the bars of the histogram. Do not allow for spaces between bars.
- For each data point, mark off one count above the appropriate bar with an X or by shading that portion of the bar.
Fishbone (Ishikawa Diagram)
Also Called: Cause-and-Effect Diagram, Ishikawa Diagram
Variations: cause enumeration diagram, process fishbone, time-delay fishbone, CEDAC (cause–and–effect diagram with the addition of cards), desired–result fishbone, reverse fishbone diagram. This cause analysis tool is considered one of the seven basic quality tools.
The fishbone 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
When to Use a Fishbone Diagram
- When identifying possible causes for a problem.
- When a team’s thinking tends to fall into ruts.
Fishbone Diagram Procedure
- Materials needed: flipchart or whiteboard, marking pens.
- Agree on a problem statement (effect). Write it at the centre right of the flipchart or whiteboard. Draw a box around it and draw a horizontal arrow running to it.
Brainstorm the major categories of causes of the problem. If this is difficult to use generic headings:
- Machines (equipment)
- People (manpower)
- Write the categories of causes as branches from the main arrow.
- Brainstorm all the possible causes of the problem. Ask “Why does this happen?” As each idea is given, the facilitator writes it as a branch from the appropriate category. Causes can be written in several places if they relate to several categories.
- Again ask “Why does this happen?” about each cause. Write sub-causes branching off the causes. Continue to ask “Why?” and generate deeper levels of causes. Layers of branches indicate causal relationships.
- When the group runs out of ideas, focus attention to places on the chart where ideas are few.
The scatter diagram graphs pairs of numerical data, with one variable on each axis, to look for a relationship between them. If the variables are correlated, the points will fall along a line or curve. The better the correlation, the tighter the points will hug the line. This cause analysis tool is considered one of the seven basic quality tools.
When to Use a Scatter Diagram
- When you have paired numerical data.
- When your dependent variable may have multiple values for each value of your independent variable.
- When trying to determine whether the two variables are related.
- When trying to identify potential root causes of problems.
- After brainstorming causes and effects using a fishbone diagram, to determine objectively whether a particular cause and effect are related.
- When determining whether two effects that appear to be related both occur with the same cause.