> ## Documentation Index
> Fetch the complete documentation index at: https://docs.pollandroll.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Merge the results of several surveys

> Merge the interviews of several surveys into a single new survey.

Merging stacks the interviews of several surveys into a **new survey**, as if they had been collected together. You get a single base, which you analyse, filter, crosstab and weight like any other survey.

The source surveys are **not modified**.

<Note>
  Merging and comparing answer different needs:

  * **Merge** — add up respondents to work on a common base (for example, stack three waves to analyse a subtarget too small in each wave).
  * **Compare** — place surveys side by side to read the gaps between them (for example, how a tracker moves wave after wave).
</Note>

## Requirements

<Steps>
  <Step title="A variable name on every question">
    The merge is performed on the **variable name** of each question. Every question in **all** selected surveys must have one. Otherwise the form rejects the merge and lists the questions at fault.
  </Step>

  <Step title="A unique variable name within each survey">
    Two questions in the same survey cannot share a variable name: the platform would not know which one to match.
  </Step>

  <Step title="Complete surveys">
    Only surveys with the **Complete** status (and demos) appear in the list. At least **two** are required.
  </Step>
</Steps>

<Tip>
  Variable names are set in the questionnaire. Fill them in as you design it: they drive merging, survey comparison and variable import.
</Tip>

## Run a merge

Merging starts from the sidebar of your workspace, under **Merge survey results** — alongside **My surveys** and **My dashboards**, outside any survey.

<Steps>
  <Step title="Select the surveys to merge">
    Pick at least two surveys in the **Surveys to merge** list.
  </Step>

  <Step title="Set the reference survey">
    The reference survey acts as the blueprint of the new survey: **only the questions present in the reference survey are merged**. It must be one of the selected surveys.
  </Step>

  <Step title="Choose the owner organization">
    It becomes the owner of the merged survey.
  </Step>

  <Step title="Validate">
    Processing runs in the background. The new survey first appears with the **Data processing** status, then switches to **Complete**. You receive an e-mail with a direct link to its results.
  </Step>
</Steps>

<Tip>
  Use the survey with the **most complete** questionnaire as reference: any question missing from the reference survey is missing from the merged survey, even if the other surveys asked it.
</Tip>

## Matching rules

* **Questions** are matched on their **variable name**, wherever they sit in the questionnaire.
* Within a question, **items** are matched on their **label**.
* **Iterations** are matched on their label, then on their rank when several labels are identical.
* Only **completes** are carried over.
* An answer with no match is not carried over: it silently disappears from the merged survey.

<Warning>
  An item label that differs from one survey to another (for example "Brand 1" and "Brand 1 B") creates **two separate items** in the merged survey. To change a label without breaking the match, use the **translation system**: it shows the new label to respondents and keeps the old one for matching.
</Warning>

## The merged survey

The new survey reuses the questionnaire of the reference survey, and its title followed by `regroup`. Rename it if needed.

It also holds a **Source** question, hidden to respondents, with **one item per source survey** (the survey title). This variable tells you where each interview comes from: filter on it to isolate one survey, or crosstab it against the questionnaire to compare the surveys inside the merged base.

**Sample sources** sharing the same name and provider are merged, and their sample sizes added up.

<Card title="Compare surveys or questions" icon="chart-column" href="/en/analyse-des-resultats/comparaisons">
  To read the gaps between waves rather than stack them.
</Card>


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