# Articles

## Full Time Equivalent Math

Full time equivalent(s), commonly referred to as FTE(s), represents the number of equivalent employees working full time. One full time equivalent is equivalent to one employee working full time. Typically, FTEs are measured to one or two decimal points. FTEs are NOT people. Rather, FTEs are a ratio of worked time, within a specific scope, like a department, and the number of working hours during a given period of time. As such, an FTE often does not equate to the number of employees actually on staff.

## Queue Math and the Danger of Averages

Flow is a key lean principle. We should relentlessly pursue a state in which value flows smoothly, without interruption to the customer. But how can this be achieved? Assuming that we have adequate system stability, repeatability, and other important "ilities," as well as a design and culture that facilitates continuous flow (admittedly, really difficult stuff), the answer is amazingly simple – match capacity to demand. So, if you have 10 customer requests your capacity should be 10 customer requests, and if the demand is 1,172 customer requests the capacity should be 1,172 requests.

## Graphs Are Math: Visual Process Performance

In the words of my friend and colleague Larry Loucka, “graphs are math.” Graphs often serve as effective visual process performance tools. Typically, these types of graphs fall into the metric category. As reflected in the supporting concepts of the fourth dimension of the Shingo Prize model, good metrics should: 1. “measure what matters,” 2. “align behaviors with performance,” and 3. “identify cause and effect relationships.” Real lean drives measurable operational and financial performance improvement.

## Balancing Two Types of Knowledge for Lean Transformation

I am halfway through reading, what I consider (thus far), an important lean book.

## ANOVA, Two Chevys, and a Ford

Analysis of Variance (most commonly referred to as ANOVA) is a common statistical test that compares the averages of several sets of data. It is unlikely for datasets to have the same average, and an ANOVA test quantifies how likely those observed differences in occurred by chance. It is a really useful test because we frequently find ourselves comparing averages of different datasets.

## Cumulative Deviation

Maybe you have a day by hour chart, or sales plan vs. actual sales data and you want an easy way to decide when to take action - consider the simple Cumulative Deviation. First you need some data, two variables that you want to compare. Here in this spreadsheet example we have Plan and Actual for eight time periods.

## Value Stream Mapping Math: Rolled throughput Yield

Value stream analysis is an effective way to identify improvement opportunities within a product or service family’s value stream, envision a leaner future state and develop an actionable value stream improvement plan to achieve the future state. It's bread and butter stuff for the lean practitioner. Most folks are well acquainted with the value stream map’s lead time ladder. And many people are familiar with the concept of rolled throughput yield.

## Plan Versus Actual Math

The plan versus actual chart is one of the most powerful and simple visual process performance metrics. In fact, it’s a sort of Swiss Army knife of charts in that it not only provides insight into process performance but, by the virtue of its comment field, begs and shares information as to when and why there is a variance from plan. Ultimately, it is about problem identification. The chart is often positioned at the pacemaker process or at the output end of a line or cell (which can be the same thing).

## Pick's Theorem (or Pick an Area, Any Area)

Pick’s Theorem is a simple way to calculate area. This theorem is particularly useful when calculating the reduction of square feet (or square meters) that was achieved by improving a process layout. To use Pick’s Theorem, overlay a sketch of the area that you want to calculate onto a square grid of points. The grid of points should be fine enough that any bend on the boundary coincides with a grid point.