UCL
Upper Control Limit (note, different from USL): representing a 3 x Sigma upwards deviation from the mean value of a variable (see also LCL). For normally distributed output, 99.7% should fall between UCL and LCL.
When used on control charts, the “3sigma” level can be calculated from sample-to-sample values or batch-to-batch averages using a “magic number,” and is used to flag-up unexpected deviations.
Unexplained Variation (S)
Regression statistical output that shows the unexplained variation in the data. Se = sqrt((sum(yi-y_bar)^2)/(n-1))
Unit
A unit is any item that is produced or processed which is liable for measurement or evaluation against predetermined criteria or standards.
Univariate
A random variable with a numerical value that is defined on a given sample space.
Voice Of the Business (VOB)
The “voice of the business” is the term used to describe the stated and unstated needs or requirements of the business/shareholders.
Voice Of the Customer (VOC)
Voice of the Customer (VOC) is a term that describes your customer’s feedback about their experiences with and expectations for your products or services. Qualtrics Voice of the Customer is a multi-source insight platform that focuses on customer needs, expectations and product improvement.
Voice of the Employee (VOE)
Voice of the Employee is the term used to describe the stated and unstated needs or requirements of the employees of your business.
It is no secret that employees who are satisfied in their jobs are more motivated, loyal, dedicated and productive.By asking your employees what they care about, you can understand motivations and perceptions to create and maintain a loyal and committed staff.
Voice Of The Process (VOP)
A term used to describe what the process is telling you. What it is capable of achieving, whether it is under control and what significance to attach to individual measurements – are they part of natural variation or a signal that needs to be dealt with?
The best way to discover the VOP is to plot it on a control chart – time sequenced events across the bottom (x-axis) and the individual results up to the side (y-Axis). Calculate the standard variation ranges and plot these as lines above and below the average the process is giving you.
Variance
Variance is a measurement of the spread between numbers in a data set. The variance measures how far each number in the set is from the mean. Variance is calculated by taking the differences between each number in the set and the mean, squaring the differences (to make them positive) and dividing the sum of the squares by the number of values in the set.
Web Chart(TM)
Graphical Visual Management Tool that Displays Multiple Measurables in a Spider “Web” like Chart Allowing Quick Analysis Among and Comparisons Between Data Streams. A Highly Effective World Class Manufacturing Visual Control Tool used in Environments such as Lean Manufacturing, Kaizen, and others. Published by the American Society for Quality in the early Nineties.
X-Bar and R Charts
X-Bar and R Charts: This set of two charts is the most commonly used statistical process control procedure. Used to monitor process behavior and outcome over time.
X-Bar and R charts draw a control chart for subgroup means and a control chart for subgroup ranges in one graphic. Interpreting both charts together allows you to track both process center and process variation and detect the presence of special causes. A user focuses on the range portion of the chart first, confirming that the process is in control. Finally, the user focuses on the average chart, looking for the special cause there.
Yellow Belt - YB
A Yellow Belt participates as a core team member or subject matter expert (SME) on a project or projects. Also, Yellow Belts may often be responsible for running smaller process improvement projects using the PDCA (Plan, Do, Check, Act) methodology. PDCA, often referred to as the Deming Wheel, enables Yellow Belts to identify processes that could benefit from improvement. These smaller Yellow Belt projects often get escalated to the Green Belt or Black Belt level where a DMAIC methodology is used to maximize cost savings using Statistical Process Control.
Y=f(X)
In this equation X represents the input of the process and Y the output of the process and f the function of the variable X.
Y is the dependent output variable of a process. It is used to monitor a process to see if it is out of control, or if symptoms are developing within a process. It is a function of the Xs that contribute to the process. Once quantified through Design of Experiment, a transfer function Y=f(X) can be developed to define the relationship of elements and help control a process.
Y is the output measure, such as process cycle time or customer satisfaction. F is the letter representing “function” (what the value(s) of X(s) does/do for Y (the output). X(s) is/are any process input(s) (variables) having assigned or inherent values(s) that is/are involved in producing the output.
Z Score
A measure of the distance in standard deviations of a sample from the mean. Calculated as (X – X bar) / sigma
Zero Defects
A practice that aims to reduce defects as a way to directly increase profits. The concept of zero defects leads to the development of Six Sigma in the 1980s.