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Multiple Data Columns

When you have multiple measurement columns, each can have its own specification limits. Quantum XL creates a separate chart and set of statistics tables for each column, stacked on one worksheet.

Goal

Run a capability analysis on both Diameter (LSL = 9.5, USL = 10.5) and Length (LSL = 24.5, USL = 25.5) in one run.

Sample Data

Press Copy for Excel, then paste the table into a blank worksheet.

Diameter Length
9.82 25.1
10.05 25.4
9.97 24.8
10.12 25.6
9.91 25.2
10.08 25.0
9.88 24.9
10.15 25.3
9.95 25.5
10.03 25.1

Each row contains paired measurements of Diameter and Length. Each column has its own specification limits.

Steps

  1. Put the data in Excel

    Press Copy for Excel above the table, click cell A1 in a blank worksheet, and press Ctrl+V. The header row lands in row 1 and the 10 data rows in rows 2 through 11.

  2. Launch the analysis

    From the Excel ribbon, select QXL Stat Tools → Analysis Tools → Capability Analysis.

  3. Select your data

    In the Data Selection window, select cells A1:B11 (the header row plus all 10 data rows across both columns). Make sure Data in Columns and First Row/Column is Header are selected, then click Next >.

  4. Configure the analysis

    In the Process Capability (Cpk) and Histogram dialog, on the Data tab:

    • Measurement Columns: "Diameter" is checked for you; also check "Length"
    • Subgroups: leave Constant size: at n = 1
    • Leave Overlay Datasets on a Single Chart unchecked, so each column gets its own chart
    • Specification Limits: the table now has one row per checked column. In the Diameter row, type 9.5 under LSL and 10.5 under USL. In the Length row, type 24.5 under LSL and 25.5 under USL

    Click Finish to generate the charts.

Result

Quantum XL creates one worksheet named Capability with two blocks stacked one below the other: the chart Capability - Diameter with its statistics tables, then the chart Capability - Length with its statistics tables. Each block uses its own column's specification limits for the LSL and USL lines, the capability indices and the PPM.

For this data, Diameter has a Cpk of about 1.06 and a Ppk of about 1.53. Length has a Cpk of about 0.31 and a Ppk of about 0.40. One Length value (25.6) is above its USL of 25.5, so the Observed row of the Length PPM table shows 100,000 PPM above the USL (1 of 10 values).