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Barry Johnson

Six Sigma

Design for Six Sigma at the Public Library

How an Oklahoma library used DFSS for landscape design and contractor selection

Published: Wednesday, July 15, 2009 - 13:43

When someone mentions design for Six Sigma (DFSS), the initial thought usually turns to developing new, innovative products. While DFSS has its roots in product development, individual components of the toolset can be applied in a variety of ways.

Recently, the use of DFSS has exploded in service industries such as health care and finance as organizations of all types strive to develop processes and products that will excite their customers. This article shares an example of how DFSS tools were used in the public service sector as one library looked to enhance the beauty of their campus.


Design for Six Sigma is a disciplined methodology with a collection of tools to ensure products and processes are developed systematically to provide reliable results that exceed customer requirements. A key function of DFSS is to understand and prioritize the needs, wants, and desires of customers, and translate those requirements into products and processes that will consistently meet those needs.

Stillwater is an innovative, growing city of approximately 50,000 residents in the plains of north central Oklahoma. As the home of Oklahoma State University’s main campus, the demographics are similar to those of other small college towns. While there is a down-home, small-town feel in the friendliness of the residents, the influence of the university is felt across the landscape, and much is expected from services such as the public library. The Stillwater public library is a wonderful asset for the community, serving not only the city, but a 30-mile radius area.

The Stillwater library campus consists of two connected buildings totaling more than 50,000 square feet, three parking areas, and a courtyard. In addition to continually investing in its collection of materials, the library invests regularly in the infrastructure to ensure it remains a source of pride for the city. One recent enhancement to the grounds was to completely relandscape the library campus.

Application of DFSS tools

As the library board discussed how they would like the grounds to be landscaped; the decision was quickly made to outsource the design and installation to a landscaping company. A professional landscaping company would have the expertise to create a design that would expand the beauty of the campus and stand up to harsh weather conditions. The board’s role would be to select the company who would maximize the value of the investment.

Because individuals or groups value different features in a product, the library board recognized different groups may be looking for various features with respect to landscaping. These different groups have various levels of importance based on the frequency that they visit the library and their interaction with the library. Prior to selecting a landscaping company, the board identified the groups that use the library and prioritized those groups to ensure they would meet the needs of the high-priority customers.

Customer groups (shown in figure 1) were identified and prioritized on a 1–9 scale, with 9 being highest priority.

Once these groups were identified, the board gathered the voice of the customer (VOC) to find out what features should be targeted for the new landscaping. The VOC was collected via direct interviews with representatives from each of the customer segments. Prior to gathering the VOC, the board met with a landscaping company to understand various aspects and options in the decision-making process that should be taken into consideration. From this, talking points were created to use as a guide during the interviews.

fig 1

Figure 1

As requirements were identified, the group expressing the issue was noted. Goals were developed for each requirement, along with the measurement to gauge the success of each requirement. Figure 2 summarizes the customer requirements.

fig 2

Figure 2

A team consisting of members of the board, library staff and patrons utilized a pair-wise comparison (see figure 3) to determine the relative importance of each requirement. This team included representatives from all of the high-priority customer segments, and they were tasked with also being mindful of the priorities of the other segments.

A pair-wise comparison forces participants to rank each item against the others in a series of A-B comparisons. While several items may be deemed important, this tool forces the team to choose which items have a higher priority (even if the relative difference is minimal). The tool adds up the number of times a particular item is chosen and calculates a weight for each item as a percentage of the total. The lowest scoring requirement is given a weight of 0.1 percent to accommodate calculations further in the process. As with most of the DFSS tools, the true value isn’t in the tool itself, but in the interaction of the team and the flow of knowledge that comes from working through the exercise. Reasons why a particular item should be ranked higher than others can be debated, allow for additional background information to be shared.

This tool is excellent for small groups (five or less) when all team members willingly participate. One risk with a pair-wise comparison, or any open discussion tool, is a dominating personality may unduly influence the outcome. If one person starts to monopolize the discussion, or if a team member does not fully participate, the facilitator may need to use some method of hidden voting so all opinions can be understood.

As the library board worked through the pair-wise comparison, the requirements of longevity/robustness of the plants and having a variety of colors rose to the top. Since Oklahoma is prone to long stretches of high temperatures during the summer months, plants that can survive extreme heat are critical to any landscape design.

fig 3

Figure 3

After the requirements were identified and prioritized, several landscaping companies submitted presentations to the board to show their design concepts for the library campus. The board then rated each company against the others with respect to each of the evaluation criteria identified by the VOC. A value-analysis (VA) template was used to capture the relative ratings.

Value analysis is an excellent tool to drive a decision when several options are available. By using this tool, the strengths and weaknesses of various concepts can quickly be identified. Where applicable, this can be an excellent tool to develop hybrid solutions to complex problems as the team draws from the strengths of various concepts.

For this example, the library board looked at each criterion, and then rated each design on its ability to deliver that requirement. A 1–9 scale was used, with a ranking of 5 as an anchor point. Higher scores indicate a favorable rating, and lower scores indicate an unfavorable rating. The value analysis created by the library board is shown in figure 4.

It is best to utilize different groups to rate the relative importance of the evaluation criteria, and to rate the relative delivery against each requirement. This eliminates biases participants may have toward a certain concept. If it is known which criteria have a bigger effect on the functional requirement score, a participant may intentionally inflate or deflate selected scores to favor their desired concept. The intent is to allow the data to drive an unbiased decision.

The relative weights of the pair-wise comparison were then fed into the VA. Each importance weighting is multiplied by the relative performance rating to give a score for each requirement for that concept. These scores are added to give an overall functional requirement score.

The cost of each concept is also added to the tool. When the functional requirement score for each concept is divided by its respective cost, a value rating is determined. If there are any constraints such as budget limitations, those should be noted on the form. Also, any other assumptions or information that may have influenced the final decision should be documented.


fig 4

Figure 4

Landscaping Inc. was the leader from a functional requirements standpoint. They outpaced the others on critical items such as longevity, variety of colors, and variety of textures. If money were not an object, this design would clearly be the winner. Although their cost was under the budget for this project, it was substantially higher than the other alternatives.

Landscaping Inc., while meeting the functional requirements better than the others, was the lowest value because of the cost. This is one advantage of conducting a VA. Oftentimes, the best functional concept that remains under the budgetary constraint is chosen. As this example illustrates, that selection method could lead to a more valuable option being passed over. On the other end of the spectrum, if cost alone had been the determining factor, Take Root Landscaping would have been selected. The risk here is this design scored very poorly on meeting the functional requirements, which could lead to dissatisfaction after implementation. When both cost and functionality were taken into account, Plants are Us proved to be the highest value.

A VA lets you understand what you are receiving in return for what your investment is. This example shows making a decision based solely on cost, meeting specific requirements, or an aggregate score based on multiple requirements could be a sub-optimal decision.

Another advantage of this tool is its ability to quickly demonstrate the effect of a change in cost, importance, or delivery of a specific requirement. Because ratings on specific requirements can be somewhat subjective, it is helpful to understand the consequences if these ratings were to change. With this tool, ratings can easily be adjusted, and the results of those changes can quickly be known.

The board used the information in the VA to negotiate with Landscaping Inc. Concessions were suggested to reduce the variety of textures and variety of colors in exchange for a lower price. Using the VA tool, the board was able to see the lower price offered by Landscaping Inc. did not sufficiently raise the company’s value rating. In the end, it was determined that Plants are Us provided the most bang for the buck and the board contracted with them to relandscape the library campus.

After implementation, the board, employees and patrons were extremely pleased with the results. The new landscaping has enhanced the beauty of the library campus, and the VA tool allowed the board to maximize the value of the investment, saving funds that can be used on subsequent enhancement projects.






About The Author

Barry Johnson’s picture

Barry Johnson

Barry Johnson serves as president of Performance Optimization Associates LLC, a performance improvement consulting group. Johnson has a bachelor’s degree in mechanical engineering from the University of Tulsa and a master’s degree in leadership from Grand Canyon University. He has more than 25 years of operations, engineering, and management experience in diverse industries such as oil and gas, automotive, consumer goods, electric utilities, and recreation. He can be contacted at barrygjohnson@sbcglobal.net.