WAVE 01
empty
Tracking studies / wave-to-wave change
Why did the wave move?
Separate a change in respondent mix from movement inside the groups. The decomposition sums exactly to the observed change — and the wording stays descriptive.
01 / UPLOAD
Two waves, same instrument
Upload a CSV for each wave. Qualtrics exports with three header rows are detected automatically; row 1 supplies the column names. Files are parsed in this browser and never uploaded to a server.
WAVE 02
empty
02 / DEFINE
Outcome, mix and weights
Choose how the outcome is defined, then choose one or two grouping columns. A second grouping column is combined into cells (for example, source × region).
Load both waves to begin.
03 / VALIDATE
Bases before conclusions
Every group is shown with its unweighted base in each wave. Groups absent from one wave and groups below the small-base threshold are flagged before the decomposition is read.
MISSING-GROUP RULE
Groups present in only one wave are retained. The absent wave is assigned the observed wave's group value, so the group contributes to composition and not to within-group change. The identity stays exact.
SMALL BASES
Groups with n < 30 in either wave are flagged. They remain in the calculation, but their contributions should be read as provisional.
04 / DECOMPOSE
The wave, bridged
REPORT
Wave comparison
WAVE 1
—
—
WAVE 2
—
—
OBSERVED CHANGE
—
—
COMPOSITION
—
Bootstrap interval pending
The part associated with a different mix of respondent groups between waves.
WITHIN-GROUP
—
Bootstrap interval pending
The part associated with group-level values moving, holding the mix fixed.
Bootstrap runs in a Web Worker after the decomposition.
WATERFALL
From wave 1 to wave 2
composition
within-group
SOURCE MIX
Who was in each wave
wave 1
wave 2
Weighted group shares. Groups present in one wave only are included.
COUNTERFACTUAL
Observed or fixed mix
HYPOTHETICAL MIX
Move the sliders
Hypothetical value applies the wave-2 group values to the normalised slider mix. Sliders always re-normalise to 100%.
05 / EXPLAIN
In plain language
CONTRIBUTIONS
Where the change comes from
Composition + within = total, by group.