Seven Basic Tools of Quality

Lecture covering basic methods in quality improvement

1. The Seven Basic Tools of Quality Brian Wells, MD, MS, MPH

2. Today’s Objectives To familiarize you with the seven basic tools of quality To provide a foundation for understanding process/operations management To provide a common vocabulary when discussing quality improvement methods

3. Seven Basic Tools of Quality The Seven Basic Tools of Quality is a designation given to a fixed set of graphical techniques identified as being most helpful in troubleshooting issues related to quality . The Seven Basic Tools stand in contrast to more advanced statistical methods such as survey sampling, acceptance sampling, statistical hypothesis testing, design of experiments, multivariate analysis, and various methods developed in the field of operations research. The seven tools are Pareto chart Cause-and-effect diagram (also known as the "fishbone" or Ishikawa diagram) Check sheet Control chart Histogram Scatter diagram Stratification Alternates: Flow chart or Run chart )

4. Pareto Chart One of the seven basic tools of quality control Contains both bars and a line graph, where individual values are represented in descending order by bars, and the cumulative total is represented by the line . The left vertical axis is the frequency of occurrence; the right vertical axis is the cumulative percentage of the total number of occurrences

5. Cause-and-Effect Diagram Ishikawa diagrams (also called fishbone diagrams, herringbone diagrams, cause-and-effect diagrams, or Fishikawa ) are causal diagrams created by Kaoru Ishikawa (1968) that show the causes of a specific event . Known as a fishbone diagram because of its shape, similar to the side view of a fish skeleton . It is used to identify possible causes for a problem. It is also used in root cause analysis (RCA) Created by first agreeing on the problem statement (effect), major causes of the problem (branches from the main arrow), asking why each happens and searching for sub-causes.

6. Ishikawa Diagram Basic Structure

7. Ishikawa Diagram Example:

8. Check Sheet The check sheet is a form (document) used to collect data in real time at the location where the data is generated. The data it captures can be quantitative or qualitative . Sometimes referred to as a concentration diagram or location plot Is the most basic statistical tool in measuring the frequency of events Best used with binary data, i.e. yes/no questions

9. Using A Check Sheet Decide what you’re going to measure Establish the time period during which you will collect data Decide whether you need to sample and, if so, what the sample size should be In many cases, you will want all relevant events

10. Check Sheet Example Tracking Medication Delays Type of Medication Delay Morning Evening Night Physician Ordering Pharmacist Approval Transportation Nurse Administration

11. Control Chart Control charts, also known as Shewhart or process-behavior charts, in statistical process control are tools used to determine if a manufacturing or business process is in a state of statistical control. Each point represents a summary statistic computed from a sample of measurements of a quality characteristic. For example, the summary statistic might be the average value of a critical dimension of five items selected at random, or it might be the proportion of nonconforming items in a sample of 100 items. The central line on a Shewhart chart indicates the average (expected value) of the summary statistic when the process is in statistical control . The upper and lower control limits (UCL and LCL) indicate the range of variation to be expected in the summary statistic

12. Control Chart Terminology

13. Control Chart Example

14. Histogram Also known as frequency distribution Graphical representation of the distribution of numerical data Used to quickly and easily demonstrate a data set’s distribution Disadvantage: Does not provide a definitive indication of a normal distribution

15. Histogram Example H istogram analysis could be used to understand the patterns of variation in electrocardiogram (EKG ) turnaround time. The average turnaround time of 8.3 days reveals relatively little information about the performance of the process .

16. Scatter Diagram A scatter plot, scatterplot, or scattergraph is a type of mathematical diagram using Cartesian coordinates to display values for typically two variables for a set of data . A scatter plot can be used either when one variable that is under the control of the experimenter and the other depends on it or when both variables are independent . If one variable is known or thought to influence the other, it is represented on the horizontal axis.

17. Scatter Diagram Generally show one of six possible correlations between the variables: Strong positive correlation (Y increases with X) Strong negative correlation (Y decreases with X) Weak positive correlation Weak negative correlation Complex correlation (Y seems to be related to X, but the relationship is not easily determined) No correlation

18. Scatter Diagram Examples

19. Stratification Stratified sampling is a method of sampling from a population Stratification is the process of dividing members of the population into homogeneous subgroups before sampling. When subpopulations within an overall population vary, it is advantageous to sample each subpopulation (stratum) independently

20. Stratification Advantages over simple random sampling: If measurements in a strata have less standard deviation, the stratification gives smaller error in estimation (ex: Amount of Lasix needed in CHF v. general population) Measurements are often cheaper/more manageable when population is grouped into strata Often desirable to have estimates of population parameters for groups within the population Disadvantage: Not useful when the population can not be exhaustively partitioned into subgroups.

21. Flowchart Allows one to draw a picture of the way a process actually works so that one can understand the existing process and develop ideas about how to improve it. High-level flowcharts are especially useful in the early phases of a project A detailed flowchart is a close-up view of the process, typically showing dozens of steps These make it easy to identify rework loops and complexity in the process

22. Flowchart Using a flowchart has a variety of benefits: It helps to clarify complex processes It identified steps that do not add value to the internal or external customer It helps team members gain a shared understanding of the process and use this knowledge to collect data, identify problems, focus discussions, and identify resources. It serves as a basis for designing new processes

23. Flowchart Flowchart example:

24. Run chart Developed by Shewart to distinguish common cause variation from special cause variation Are graphs of data over time and are one of the most important tools for assessing the effectiveness of change Have a variety of benefits Help improvement teams formulate aims by depicting how well or poorly a process is performing They help in determining when changes are truly improvements by displaying a pattern of data that one can observe as one makes changes They give direction as one works on improvement and information about the value of particular changes

25. Run Chart What makes up a run chart?

26. Run Chart What is a run? One or more consecutive data points on the same side of the median Do not include points falling on the median Non-random patterns are indicated by A shift in the data process, or too many data points in a run (6 or more consecutive points) A trend (5 or more consecutive points all increasing or decreasing) Too many or too few runs An “astronomical” data point

27. Run Chart Run example:

28. Run Chart Non-random Patterns

29. Run chart Example: