在諸如汽車業(yè)的一些產(chǎn)業(yè)中，人們將對CPK的計算稱作PPK.至于人們?yōu)槭裁从?2或者更多的數(shù)據(jù)來計算CPK，我對此做了一些研究。人們在運(yùn)算中視cp1.33為普通理解與當(dāng)前能力與4sigma的離差保持一致。如果你用這個數(shù)據(jù)做一些計算然后對照美國質(zhì)量出版社出版的表格。(我曾嘗試著郵寄那張表，但都沒有成行。這簡直太糟了，我猜想管理部門遺失了該郵件)。你可以取值接近32，但即使32有時候也不足以得到一個沒有誤差的加工能力比率

　　What I wanna stress again is that capability ratio is not everything， there are too many misuses in the industry， don‘t count all on it.

　　我想再一次強(qiáng)調(diào)的是加工能力比率并不是萬能的，在工業(yè)上有很多的誤用，不要全部依靠它來計算。

　　Here is my answer to the question of 32 sample size：

　　這里是我對樣本尺寸為32的問題的回答。

　　A practice that is increasingly common in industry is to require a supplier to demonstrate process capability as part of the contractual agreement. Thus， it is frequently necessary to prove that the process capability ratio Cp meets or exceeds some particular target value——say， Cp0. This problem may be formulated as a hypothesis testing problem：

　　一個要在工業(yè)中日漸成熟的練習(xí)是需要一個供應(yīng)者示范如契約的協(xié)議部份般的程序能力。 因此，有必要經(jīng)常證明加工能力比率CP等于或者超過如CP0的一些特殊目標(biāo)價值。這個問題可能被制定為一個假設(shè)的測試問題：H0：Cp= Cp0 (or the process is not capable)

　　H1： Cp≥ Cp0 (or the process is capable)

　　We would like to reject H0 (recall that in statistical hypothesis testing rejection of Null hypothesis is always a strong conclusion)，thereby demonstrating that the process is capable. We can formulate the statistical test in terms of Cp‘，so that we will reject H0 if Cp’ exceeds a critical value C.

　　我們想要否定H0( 取消對統(tǒng)計的假設(shè)中無效力假設(shè)的測試否定一直是一個強(qiáng)大的結(jié)論)。因此，示范加工是有能力的。我們可以根據(jù) Cp‘ 制定統(tǒng)計的測試， 所以如果 Cp’超過一個關(guān)鍵的價值 C，那么我們會否定H0 .

　　Kane(1986) has investigated this test， and provide a table of sample sizes and critical values for C to assist in testing process capability. We may define Cp(High) as a process capability that we would like to accept with probability (1-α) and Cp(low) as a process capability that we‘d like to reject with probability (1-β)。 Please refer to the table created by Kane and used by American Society for Quality Control.

　　凱恩 (1986) 已經(jīng)調(diào)查這上述測試， 而且向C提供一張有樣品大小和關(guān)鍵值的表給來協(xié)助測試的加工能力。就如我們喜歡接受(1-α)的可能性和CP(低)作為程序能力和否定(1-β)的可能性一樣，我們可以將CP(高)定義為一個加工能力。請查閱凱恩所創(chuàng)建的并為美國社會質(zhì)量控制所用的表格.考試通