σ水平、公差T、CPk水平与不良品率的关系一览表%T1666.7%769.2%625.0%4.5%357.1%303.0%285.7%263.2%250.0%232.6%222.2%208.3%196.1%192.3%188.7%185.2%181.8%178.6%175.4%172.4%169.5%166.7%163.9%161.3%158.7%156.3%153.8%151.5%149.3%147.1%144.9%142.9%140.8%138.9%137.0%135.1%133.3%131.6%129.9%128.2%126.6%125.0%123.5%122.0%120.5%119.0%117.6%116.3%114.9%113.6%112.4%111.1%109.9%108.7%K（σ）0.180.390.480.660.840.991.051.141.21.291.351.441.531.561.591.621.651.681.711.741.771.81.831.861.1.921.951.982.012.042.072.12.132.162.192.222.252.282.312.342.372.42.432.462.492.522.552.582.612.2.672.72.732.76Cpk0.060.130.160.220.280.330.350.380.40.430.450.480.510.520.530.0.550.560.570.580.590.60.610.620.630.0.650.660.670.680.690.70.710.720.730.740.750.760.770.780.790.80.810.820.830.840.850.860.870.880.0.90.910.92PPM800000.00700000.00600000.00500000.00400000.00317310.00293800.00250000.00230200.00200000.00177000.00150000.00126016.73118759.88111834.81105232.242.9492957.3287265.8781859.0276727.1471860.67249.9462885.5358757.96857.9051176.1247703.5344431.1941350.3338452.3435728.8433171.6130772.6728524.24218.7724448.9522607.6920888.1519283.7417788.0916395.0715098.82133.7012774.3111735.4810772.299880.0390.228290.607585.126933.956333.435780.14%T107.5%106.4%105.3%104.2%103.1%102.0%101.0%100.0%99.0%98.0%97.1%96.2%95.2%94.3%93.5%92.6%91.7%90.9%90.1%.3%88.5%87.7%87.0%86.2%85.5%84.7%84.0%83.3%82.6%82.0%81.3%80.6%80.0%79.4%78.7%78.1%77.5%76.9%76.3%75.8%75.2%74.6%74.1%73.5%73.0%72.5%71.9%71.4%70.9%70.4%69.9%69.4%69.0%68.5%K（σ）2.792.822.852.882.912.942.9733.033.063.093.123.153.183.213.243.273.33.333.363.393.423.453.483.513.3.573.63.633.663.693.723.753.783.813.843.873.93.933.963.994.024.0.084.114.144.174.24.234.2.294.324.3.38Cpk0.930.940.950.960.970.980.9911.011.021.031.041.051.061.071.081.091.11.111.121.131.141.151.161.171.181.191.21.211.221.231.241.251.261.271.281.291.31.311.321.331.341.351.361.371.381.391.41.411.421.431.441.451.46PPM5270.84802.3371.923976.753614.293282.1229782699.82445.2213.372001.561808.511632.71472.751327.351195.31075.47966.85868.46779.42698.93626.21560.59501.41448.11400.13356.98318.22283.42252.22224.25199.22176.83156.83138.97123.03108.8496.1984.9574.9566.0758.251.2245.0439.5734.7330.4626.6923.3720.4417.8715.613.6111.87%T68.0%67.6%67.1%66.7%66.2%65.8%65.4%.9%.5%.1%63.7%63.3%62.9%62.5%62.1%61.7%61.3%61.0%60.6%60.2%59.9%59.5%59.2%58.8%58.5%58.1%57.8%57.5%57.1%56.8%56.5%56.2%55.9%55.6%55.2%.9%.6%.3%.1%53.8%53.5%53.2%52.9%52.6%52.4%52.1%51.8%51.5%51.3%51.0%50.8%50.5%50.3%50.0%K（σ）4.414.444.474..534.5.594.624.6.684.714.744.774.84.834.8.4.924.9.985.015.045.075.15.135.165.195.225.255.285.315.345.375.45.435.465.495.525.555.585.615.5.675.75.735.765.795.825.855.885.915.945.976Cpk1.471.481.491.51.511.521.531.1.551.561.571.581.591.61.611.621.631.1.651.661.671.681.691.71.711.721.731.741.751.761.771.781.791.81.811.821.831.841.851.861.871.881.1.91.911.921.931.941.951.961.971.981.992PPM10.3497.826.85.95.124.433.843.322.872.482.141.841.591.371.171.010.860.74210.63580.430.46550.39780.33970.270.24690.21030.170.15210.12920.10960.09290.07870.06660.050.04760.04020.03390.02860.02410.02020.0170.01430.0120.010.00840.0070.00590.00490.00410.00340.00290.00240.002Note: 1、 available for bilateral tolerance (双向公差适用）
2、 k（σ）对应于控制范围，σ是实际的计算值，如果客户规范公差范围对应的k值是2.34，对应的cpk是0.78，不良品率=19283ppm 3、 %T是实际控制6 σ占规范公差T的比例，假如实际6σ等于规范公差T，则CPk=1.0。CPK要达到1.33的水平，6σ=T*75%。 4. T%中的T是指±T中的T，而不是指整个公差带
举例： 1、 客户公差范围T=5，我们内控6σ范围=4，则%T=80%，对应的CPK=1.25，不良品率=175.8ppm 2、 实际的CPK=0.83，控制范围：±2.49σ，按6sigma理论则是5sigma。 3、 6sigma项目是指CPK2.0，公差带内需能容纳12σ（±6σ).
