Compute the theoretical DPMO using the normal distribution. Is this a reasonable calculation? If yes, why? If no, why not? Answer: DPO = 0.0112 DPMO = 1,000,000 x 0.0112 = 11,200 The DPMO…

Question

Options

• AYes, because the calculated DPMO of 11,200 is acceptable.
• BNo, because the process is not stable at this time.
• CYes, because the DPO calculation is correct.
• DNo, because the normal distribution cannot be used for DPMO.

• A
  12% (4)
• B
  59% (20)
• C
  24% (8)
• D
  6% (2)

Explanation

Option B is correct because computing a theoretical DPMO using the normal distribution assumes the process is in statistical control (stable). When a process is unstable, its variation is unpredictable, so fitting a normal distribution to the data produces a meaningless capability estimate - the math works, but the result doesn't reflect reality.

Option A is wrong because whether 11,200 DPMO is "acceptable" is irrelevant to the validity of the calculation; reasonableness depends on statistical prerequisites, not the numerical outcome. Option C is wrong because correctly computing DPO is only one step - the calculation is still unreasonable if the foundational assumption of process stability is violated. Option D is wrong because the normal distribution can legitimately be used for DPMO; the problem here isn't the choice of distribution, it's that the process doesn't meet the stability precondition.

Memory tip: Think "Stable before Capable." You must confirm statistical stability (control chart in control) before performing any theoretical capability analysis - DPMO, Cpk, or otherwise. No stability = no valid capability number.

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