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Problem tree is somehow similar to creating mind maps to identify the root cause as well as the downstream effect of a problem in a more structured way. There are a few key rules we should consider to make a decision tree to drill down from CTQ to project big Y. First step is to define the Goal and the to add potential decisions and outcomes. Similar to how you create a Ishikawa diagram using 5 why approach. Once you have the CTQ well defined then you can prioritize the causes/outcomes to act upon. For a black belt to decide when to stop and finalize the Project Y depends on several factors, including the project scope, resources available, and the desired level of improvement. Basically his role is to check & ensure that project Y is aligned to defined goals and we are utilizing all possible resources as per the agreed/defines timelines. Also to track & evaluate the effectiveness of improvement efforts though metrics/kpi’s. If there is any deviation observed by the black belt in any of the above listed factors the project can be stopped or finalized.

Problem Definition Tree: CTQ Drill down or Problem Definition Tree diagram relates high level focal points(Resultant output)to project objective(factors) The measure of those items linked to the CTQ are called Project Y. The following situations mandates the Problem definition Tree to be applied: 1.When Project Indication is vague without knowing which parameter need to be improved. 2.When parameters of Big Ys are defined from customer perspective rather than process control perspective. 3.When dimensions of the Big Ys are aimed at abstract terms and not in tangible terms. In General ,The following rules can be applied while splitting the Big Ys to Project Y : 1st Rule – Boxes in a split should not overlap. Need to respect the parent dictionary and divide it into subgroups 2nd rule – Need to ensure that sub groups selected must encompass the whole dictionary . 3rd Rule – Boxes or sub groups must be able to provide us with details and data needed for running experiments. The Black belt should finalize the last unbreakable activity or component which can contribute to the Big Y and select this item as Project Y. This is the actionable item which need to be acted upon to improve the Project Y and thus the Big Y to solve Let us take example of OEE Overall Equipment efficiency not achieved the Target for may '23( Big Y) and drill down to find the project Y - which contributes the highest , so that action can be initiated immediately . The injection molding machine shop OEE is 84% , which is average of 3 machines OEE #1,#2,#3.However target is 90%. In this Example - the black belt has to stop here and take a call, after he had broken down the Big Y to actionable items or factor KPIs, at the activities contributing to availability loss of M/C #2 - out of the which Top 3 activity can be taken as Project Ys .Thus we have divided our Big Y of OEE Target not achieved problem into many Project Ys and Black Belt can stop here as below to finalize projects for further working by small work groups on each . Here Changeover Time is the 1st actionable item to be worked on followed by Breakdown time reduction & material shortage issue reduction. Once all these Project Ys are addressed , eventually the Big Y ( OEE of molding) would be achieved. Problem definition Tree clearly gives us direction, focus. 1.Change over time - 45% 2.Breakdown Time - 22% 3.Raw material shortage time - 18% The General criteria/steps to be used while splitting boxes. 1.Use Logic to make splits ( using creative & alternate searches) 2.Never move to next level until , all important in the family is identified. 3.Make Broad splits first and detailed splits later - Avoid going into the factor x , until the detailed split of Ys 4.FInally use facts and physical laws of logical correlation to make decision vis cause/effect matrix.

To create an effective Problem Definition Tree, a Black Belt should: Focus on specific and measurable outcomes. Prioritize actionable objectives. Maintain logical connections. Avoid overlapping or redundant objectives. Limit the number of levels. Use factual data and evidence. Iterate and refine as needed. When deciding at which level to stop and finalize project Y, a Black Belt should consider: Project goals and objectives. Stakeholder satisfaction. Time constraints. Budget considerations. Change in scope or organizational priorities. Clear identification of the problem statement and process improvements. Statistical significance. By considering these factors, a Black Belt can make an informed decision on whether to stop and finalize project Y at a particular level or continue with further improvements.