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Knowledge Challenge
A friend thinks you can answer this question about Statistical Process Control
Your weekly customer churn rate has been: 2.1%, 2.4%, 2.0%, 2.3%, 2.2%, 2.5%, 1.9%, 2.4% (mean ~2.2%, σ ~0.2%). This week it's 2.6%. Three months ago it ran 1.8-2.1%. What does SPC suggest?