Estimating the precision of a measurement system

Estimate the precision of a measurement system or procedure.

  1. Select a cell in the dataset.
  2. On the Analyse-it ribbon tab, in the Statistical Analyses group, click Precision, and then click:
    Option Description
    Simple Measurements are made under the same conditions.
    1 Factor Measurements vary by a single random factor.

    Use for performing CLSI EP5 or EP15 in a single laboratory with Run as a factor.

    2 Factor Nested Measurements vary by 2 random factors.

    Use for performing CLSI EP5 in a single laboratory with Day and Run as nested factors.

    3 Factor Nested Measurements vary by 3 random factors.

    Use for performing CLSI EP5 in multiple laboratories with Laboratory, Day, Run as nested factors.

    The analysis task pane opens.
  3. In the Y drop-down list, select the measured quantity variable.
  4. If required: In the Factor A drop-down list, select the first random factor.
  5. If required: In the Factor B nested within Factor A drop-down list, select the second random factor that is nested within the first factor.
  6. If required: In the Factor C nested within Factor B drop-down list, select the third random factor that is nested within the second factor.
  7. Optional: If there are multiple levels of measurement, in the By drop-down list, select the level variable.
  8. Optional: To label the conditions of measurement for the innermost and outermost nested factors, in the Conditions drop-down list, select the labels.
  9. Optional: To customize the detail of the output, select or clear the Abbreviated and Detail check boxes as appropriate.
  10. Optional: To compare the precision against performance requirements:
    • If the allowable imprecision is a constant or proportional value across the measuring interval, under the Allowable imprecision group, select Across measuring interval, and then in the SD / CV edit box, type the SD in measurement units, or the CV as a percentage (suffix with % symbol).
    • If the allowable imprecision varies for each level, under the Allowable imprecision group, select Each level and then in the Allowable imprecision grid, under the SD / CV column, alongside each level, type the SD in measurement units, or the CV as a percentage (suffix with % symbol).
    Note: To compare precision against a performance claim, see Testing precision against a performance claim.
  11. Click Calculate.