If you apply either a prioritisation technique (e.g. ranking), or just go for what the team feels to be the most vital effects in order to reduce the number of metrics you have, then you run the risk of intentionally ignoring a factor which may be the solution.
Presumably you are doing this 6S project because you do not yet know the answer to your problem?
Before you take a huge leap of faith in your ability to detect solutions randomly, then I would suggest that you collect sufficient data to enable an informed decision to be made as to which metrics can safely be ignored. Yes it can be expensive, but so can taking the wrong decision early in a project.
Just my half-penny’s worth.
James A
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