Bar chart
A bar chart is a plot of categorical variables, and the discontinuity should be indicated by having gaps between the rectangles. Often this is neglected which may lead to a bar chart being confused for a histogram.


Check sheet
A structured, prepared form for collecting data.

Cluster sampling
With cluster sampling, the investigator will divide the population into separate groups called clusters. Then, a simple random sample of clusters is selected from the population. The researcher conducts the analysis on data from the sampled clusters. Typically used when "natural" but relatively homogeneous groupings are evident.

Concentration diagram
A graphical tool that is useful in revealing patterns of problem occurrence especially where problems occur in physical systems or facilities.

A drawing of the product, place (or other item of interest), is constructed with all relevant views displayed, onto which the locations and frequencies of various defects or problems are shown.

Action or actions taken to rectify a problem.


Data analysis
A process of assessing, inspecting, modelling results with the goal of discovering useful information, suggesting conclusions, and supporting decision making.

Data collection
The process of gathering information in an established systematic fashion that will enable one to answer stated research questions, test hypotheses, and evaluate outcomes and trends.

Data, information
Data (typically numerical) are collected and analysed to create information suitable for making decisions. Data becomes information by interpretation, e.g. the height of Mt. Everest is generally considered as 'data', a book on Mt. Everest geological characteristics may be considered as 'information'.

Deming wheel
An iterative four-step management method used in business for the control and continuous improvement of processes and products. Illustrated as a PDCA wheel (plan–do–check–act or plan–do–check–adjust).


Fishbone diagram
A diagram (shaped like a fish bone) that shows the causes of an event, it is often used in manufacturing and product development to outline the different steps in a process or it can be used to help identify areas that may be investigated as part of root cause analysis.

5 Whys
A question-asking technique used to explore the cause-and-effect relationships underlying a particular problem. The primary goal of the technique is to determine the root cause of a defect or problem.

Failure, Mode, Effect, Analysis.

A systematic technique for failure analysis. It involves reviewing as many components, assemblies, and subsystems as possible to identify failure modes, and their causes and effects.

An FMEA is mainly a qualitative analysis.


A histogram displays data that has been grouped into ranges (such as 0-10°C, 11-20°C, 21-30°C, 31-40°C), and then plotted as bars. Histograms are often confused with bar charts. They are similar but in a histogram each bar represents a range of data.


A point where two systems, subjects, organisations, departments etc. meet and interact.

Also known as a PEM PEM or Fishbone diagram.

A diagram (shaped like a fish bone) that shows the causes of an event, it is often used in manufacturing and product development to outline the different steps in a process or it can be used to help identify areas that may be investigated as part of root cause analysis.


Management Oversight Risk Tree (MORT)
Method of problem analysis developed by NASA.

Mind mapping
A more structured visual form of note taking that offers an overview of a topic and its complex information, allowing one to comprehend and build connections.

Multi-disciplinary team
A group of people working together from different areas of the business to guide, advise and share their learning or expertise.


Failure to conform to/be not in accordance with an established method, rule or procedure.


Pareto chart
A Pareto chart, named after Vilfredo Pareto, is a type of chart that contains both bars and a line graph. Individual values are represented in descending order by bars, and the cumulative total is represented by the line.

A problem solving process.

Preventative action
Action or actions taken to stop the recurrence of an issue or problem.


Random sampling
A method applied when a subset of data (a sample) is chosen from a larger set (a population). Each subset of data is chosen randomly and entirely by chance, such that each subset of data has the same probability of being chosen at any stage during the sampling process, and each subset of individuals has the same probability of being chosen for the sample as any other subset of individuals.

Representative data
A subset of a statistical population that accurately reflects the members of the entire population. A representative sample of data should be an unbiased indication of what the whole population is like.

Root Cause
An unwanted issue that, once removed from the problem fault sequence, prevents the final undesirable event from recurring.

Root Cause Analysis (RCA)
A method of problem solving that tries to identify the root cause of faults or problems.


Scatter chart
A type of mathematical diagram using Cartesian coordinates to display values for two variables for a set of data.

The extent of the area or subject matter that something deals with, e.g. a summary of what is to be investigated as part of the Root Cause Analysis study.

In an example where a food poisoning outbreak had occurred in a foodservice establishment, too small / general a scope might be, 'Investigation into a Listeria outbreak at WXY Chicken Shack'. The documented scope needs to: precisely define the issue; the scale of the problem; the date(s); considerations and potential contributing factors; location and impact. It must also not dismiss anything that may later form part of the investigation.

A better scope in this instance may be, 'Investigation into hygiene, cleaning, storage, material handling and other practices that may have led to a Listeria monocytogenes outbreak on December 24th 2015 at WXY Chicken Shack, Poultry Lane, Hensville, resulting in the hospitalisation of 3 customers'.

Six Thinking Hats
A tool created by Edward de Bono.

A framework to help people think clearly and thoroughly by directing their thinking attention in one direction at a time. Members of a group wear a coloured hat. The six hats are different colours and each signals the thinking ingredient: white hat facts, green hat creativity, yellow hat benefits, black hat cautions, red hat feelings, and blue hat process.

The technique should encourage decisions from a number of important perspectives (considering the facts, benefits, process etc) and force people to move outside their habitual thinking style. It is thought to achieve a more rounded view of a situation.

A means of solving a problem.

Stratified sampling
When a population is divided into groups, taking a stratified sample ensures that a sample is taken from each group in the correct proportion.

Example. You want to take 8 hand swabs from staff at a dairy. The dairy operates 3 shifts, how many hand swabs should be taken from each shift?

Early shift: 19
Day shift: 22
Late shift: 8

The total number of staff is

19 + 22 + 8 = 49

To find the number of hand swabs to be taken from staff on each shift, you multiply the number of staff on each shift by (sample size divided by total population) (which in our example = 0.16).

Early shift = 3, Day Shift = 4, Late Shift = 1.

An indication of the existence of something, typically of an undesirable issue.

Systematic sampling
This is random sampling with a system. From the sampling frame, a starting point is chosen at random, and choices thereafter are at regular intervals. The most common form of systematic sampling is an equal-probability method.

In this approach, progression through the list is treated circularly, with a return to the top once the end of the list is passed. The sampling starts by selecting an element from the list at random and then every kth element in the frame is selected, where k is the sampling interval. This is calculated as:


where N is the population size and n is the sample size.

Example: Suppose you want to sample 20 temperature records from a month of 100 records. 100/20=5, so every 5th temperature record in the month is chosen after a random starting point between 1 and 5. If the random starting point is 3, then the records selected are record number 3, 8, 13, 18, 23, 28, 33, 38, 43, 48, 53, 58, 63, 68, 73, 78, 83, 88, 93 and 98.


Thought shower
To work in a group or individually to produce ideas around a topic.

Trend analysis
Techniques that use historical information data to determine if a trend exists and, if so, what the trend indicates.

see Trend Analysis.