The Capability Analysis (Weibull) generates a process capability report containing various capability indices. It is used when the data is from a Weibull distribution. This procedure also generates a histogram of the data with a Weibull curve.
1. Choose ProcessMA > Quality Tools > Capability Analysis > Capability Analysis (Weibull).
2. In Variable, select the column containing the data.
3. In Lower specification limit, enter the lower specification limit (at least one specification limit is required).
4. In Upper specification limit, enter the upper specification limit (at least one specification limit is required).
Optional
5. In Historical shape, enter the historical shape parameter value.
6. In Historical scale, enter the historical scale parameter value.
7. In Target, enter the target value.
8. In Sigma tolerance, enter the interval (number of standard deviations) to calculate the capability statistics, otherwise 6 standard deviations will be used.
Note To select a column of data into a textbox, double-click on any of the column names shown in the list on the left of the dialog box while in the textbox.
Variable: Numeric.
Historical shape: Numeric.
Historical scale: Numeric.
Target: Numeric.
Sigma tolerance: Numeric.
You are an engineer and you need to ensure the electrical stability of circuit boards. You recorded the length of time the circuit boards were unstable while being plugged in for a period of 30 days. You want to run a capability cnalysis based on the Weibull distribution.
1. Open worksheet ProcessMA > Tools > Data Files > Control.xls.
2. Choose ProcessMA > Quality Tools > Capability Analysis > Capability Analysis (Weibull).
3. In Variable, select M – Unstable.
4. In Upper specification limit, enter 3.
5. Click OK.
