Home / Statistical Tools / MSA / Nested / Options

Options¶

Every control on the Nested dialog. The dialog has three tabs in a nested study: Data, Options and Gage Info. The Model tab and the Extended options group belong to an Extended study and are not shown here.

The dialog is the same one the Crossed study uses, so the controls are identical except that the XbarR estimation method is unavailable.

Data tab¶

Two radio buttons at the top of the tab choose where the data come from:

Excel reads the range you selected on the worksheet.
GroupBy reads the same range but splits it into groups first, and runs a separate complete analysis for each group.

A problem with the current selections is reported in red near the top of the tab, above the role lists. The message stays until the selections satisfy it, so the tab is worth re-reading from the top when Finish does not do what you expect.

Data Types¶

Data Types lists every column in the selected range with a drop-down setting its type. The type decides which role lists the column is offered in below, so a column that will not appear where you expect is usually typed wrongly here.

The available types are Continuous, Nominal, Count, Integer and DateTime.

Measurement Columns¶

Measurement Columns is the list of columns holding the measured values. Tick one column per characteristic you want analysed. This list accepts more than one column, unlike the role lists below it.

Each measurement column is a complete analysis of its own

Ticking three measurement columns does not produce one report covering three characteristics. It produces three separate worksheets, each a full analysis of one column: its own Gage R&R table, its own analysis of variance, its own charts.

In GroupBy mode the two multiply. Three measurement columns across four groups produce twelve worksheets.

Part¶

Part is the column identifying which part each measurement was taken on. It is required, and exactly one column can be chosen.

Operator (Optional)¶

Operator (Optional) is the column identifying who or what took each measurement. Its label says optional and it means it: a study with no operator column runs, and reports repeatability and part to part variation without a reproducibility component to separate out.

Exactly one column can be chosen. Parts of the report depend on this column being present, and each is simply absent without it: the reproducibility rows, the Measurement by Operator chart, the box plot by operator, and the Part by Operator Interaction chart.

The average and range charts are not among them. Without an operator column they are still drawn, grouped by part alone and carrying a single series each instead of one series per operator.

Reference (Optional)¶

Reference (Optional) is the column holding the known true value of each part. Exactly one column can be chosen, and it must be numeric.

Supplying it turns on the bias and linearity part of the analysis, which is the only part that can say whether the measurement system reads correctly rather than merely consistently. Without it, the bias and linearity tables and the Linearity and Bias charts are absent.

Specification Limits¶

Specification Limits is a small grid with one row for each measurement column you ticked, and columns headed Column, LSL and USL. Each characteristic gets its own limits, because each becomes its own worksheet.

Either limit can be left empty. What the limits control:

Supplied	Effect
both	the tolerance width is the upper limit minus the lower
one	the tolerance width is twice the distance from the study mean to that limit
neither	every percent of tolerance column, the precision to tolerance ratio, the whole misclassification block, the gage performance curve and the sweep charts are all absent

A row with a problem in it is highlighted, and the reason is available as a tooltip on the row. A lower limit that is not strictly below its upper limit is refused.

GroupBy¶

Choosing GroupBy reveals the grouping panel: Available Items on the left and GroupBy Order on the right. Between the two lists, > moves the selected column across and >> moves all of them, with < and << moving them back. To the right of the second list, ^ and v change the position of a column within GroupBy Order, which is the order the grouping is applied in. A DateTime column additionally gets a drop-down choosing how its values are grouped.

Each distinct combination of the grouping columns becomes its own complete analysis on its own worksheet, and each worksheet names its group.

This is the same grouping panel used throughout Quantum XL, and it behaves the same way here.

Selecting a column shows a line of information about it at the foot of the tab. It is there to confirm you picked the column you meant and it changes nothing about the analysis.

Options tab¶

Estimation Method¶

The Estimation Method group chooses how the variance components are computed. All four choices report the same set of quantities where they can compute them; they differ in how they get there and in what they cannot produce.

Automatic (balanced: EMS; unbalanced: REML)

Automatic (balanced: EMS; unbalanced: REML) is the default. It uses the expected mean squares method when the data are balanced and restricted maximum likelihood when they are not.

Balanced means every cell of every model term holds the same number of measurements and none is empty. A single missing measurement is enough to make a study unbalanced, which is the usual reason this setting picks REML.

Restricted Maximum Likelihood (REML)

Restricted Maximum Likelihood (REML) estimates every variance component at once from the data as a whole, under the constraint that a variance cannot be negative.

Two things follow that the other methods do not offer:

It reports confidence intervals on unbalanced data as well as balanced.
It never reports a negative estimate floored to zero, because it never computes a negative one. A reported zero means the constrained estimate reached the zero boundary.

It also has one limit: it cannot fit a model with a term involving more than three factors once nesting is counted. Where that happens the analysis uses expected mean squares instead, and the Model tab warns before you run it.

Expected Mean Squares (EMS) - Equivalent to ANOVA when balanced

Expected Mean Squares (EMS) - Equivalent to ANOVA when balanced builds the analysis of variance table and solves for the components from the mean squares.

As the label says, on balanced data this gives the same answers as the classical analysis of variance, which is what makes it the method to choose when the numbers need to match a hand calculation or a published example.

Two consequences worth knowing before choosing it:

A component's estimate can come out negative. Zero is reported in its place, with a footnote saying so and suggesting REML.
On data that is not balanced this method reports no confidence intervals at all. Balanced data under this method keeps its full set of intervals.

XbarR

Not available for a nested study. The radio button is disabled and the reason is shown beneath it. The method forms part and operator cells, and a nested layout has none: no part appears under more than one operator. Choose one of the three methods above instead.

The report states the method that was actually used

The Estimation method: row near the top of the report names the method the analysis ran with, not the one selected in this group. The two differ when Automatic made the choice, and when a model REML cannot fit caused the analysis to fall back to expected mean squares.

Analysis Options¶

Misclassification sweep charts

Misclassification sweep charts adds the charts that show how the misclassification probabilities would change if the process mean moved. The mean is swept across a range measured in part to part standard deviations and each probability is recomputed at every step.

The charts need at least one specification limit, so they are absent without one whatever this box says. A Crossed or Nested study gets the two joint-probability sweeps; an Extended study gets all five.

Part Variation is Not Representative of the Population

Part Variation is Not Representative of the Population is for a study whose parts were not chosen to span the range the process actually produces, for example a set of parts gathered from one shift or deliberately picked to be similar. When the parts do not represent the process, every statistic that compares the gage against part to part variation describes the sample of parts rather than the process.

The dialog's own tooltip states exactly what the option does:

Display-only: hides part-to-part variation and every statistic derived from it (total variation, % contribution, % study variation, ndc, misclassification). Does not change what the engine computes.

This option hides, it does not recompute

Every number that remains is the same number it would have been with the box clear. Nothing is re-estimated and no component changes. What is withheld is the part to part variation and the statistics that divide by it, because those are the ones a non-representative set of parts makes misleading.

The percent of tolerance columns are not withheld, because they compare against the tolerance rather than against the parts. That is also why the misclassification block and its sweeps come back when a historical standard deviation was supplied and used: the process variation then comes from the historical value instead of from the parts in the study.

Interaction removal¶

Interaction removal runs by default on every study

Quantum XL drops interaction terms the data give no evidence for, pooling each removed term's degrees of freedom and sum of squares into repeatability. This happens by default in a Crossed and a Nested study as well as an Extended one, at a p-value threshold of 0.25.

Only an Extended study can change it. The Remove insignificant interactions checkbox and its Alpha: field sit in the Extended options group, so a Crossed or Nested study always runs with removal on at 0.25.

You can see whether anything was removed: when a term is dropped the report carries two analysis of variance tables rather than one, and the removed term is marked in the first.

Removal is turned off automatically when the data have no replicates, and the report notes that.

Gage Info tab¶

The Gage Info tab records seven free-text fields describing the gage and the study: Gage name:, Gage no.:, Gage type:, Part name:, Part no.:, Date: and Performed by:.

They are copied onto the report and enter no calculation. Every one can be left empty. They are there so a printed report identifies the gage and the study it came from without needing a separate record.