Sometimes you may need to perform analyses using data from multiple data files. For example, create crosstabs using questions between two data files, analyze wave-over-wave data, combine data files with multiple waves, or analyze non-overlapping data sets at the same time.
Depending on the setup and relationship between the data files, you have options in Q. The table below will help you decide which method to use when working with multiple data files.
| Method | Description | When to use | Examples |
| Merging data involves combining the data between two files where you are either adding new cases (respondents) or appending new variables. | When you want to combine data from an ongoing study, a tracking project, or when you've added new questions to an existing project. |
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| Create a Data File Relationship |
Connect two files without merging into a single data file. Typically, these files are linked using a common ID variable. |
When you want to compare data between two data files that do not have overlapping questions or variables. |
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| Data Fusion | Data fusion, also known as statistical matching, involves combining the data from two files where the sample between the two files does not overlap. | When you want to combine data from two different studies. | If one study looks at customer satisfaction and a separate study looks at brand attitudes, data fusion can be used to combine the data. |