Once you have gotten your data into Displayr, it is necessary to check that the data is all as you expect. This is typically something of a never-ending process, but the following basic checks are the minimum:

- Sample size
- Checking that the file only contains completed interviews
- Grouping of variables into variable sets

## Sample size

To review the sample size of a data file, click the data set in the **Data Sets tree**, and the sample size is shown as the **Number of cases** in the **object inspector** on the right side of the page. In the example below, the sample size is 300.

## Complete interviews

Sometimes data file contains incomplete interviews. In general, it is typical practice to remove such interviews prior to performing any analysis. Sometimes data files will contain a variable that indicates which interviews were complete. In other situations, the way to check is to create a table using the data from the last question in the study that was meant to be asked of everybody.

To create a table of the last question in the study in Displayr, scroll down to the bottom of the **Data Sets tree** and drag the variable onto the page. The sample size will be shown in the footer at the bottom of the table.

## Correct grouping of variables into variable sets

The underlying structure of a data set is a large table, where each row represents the data for each person to complete the survey, and each column represents some property of the people. These columns are commonly referred to as *variables. *

Displayr automatically groups variables into *variable sets *of related variables. Often these variable sets will contain only a single variable. However, they can contain multiple variables. This is useful as when variables are grouped together, Displayr will both allow you to automatically manipulate them all at the same time, and will automatically summarize them all at the same time when creating tables.

In the example below, the triangle to the left of **Race **tells us that it contains more than one variable (the triangle appears when you hover over the data set).

When you click on the triangle, the variable set is expanded, and we can see all the variables within it.

More info on how to combine variables in to variable sets, their structure (how they appear in tables), and value attributes (the categories and values used in calculations) can be found on our Variable Sets page.

## Next

If the data set looks OK, the next step is to learn the basics of Displayr.

Otherwise, it is necessary to either:

- Obtain a better data file and import this.
- Clean the data.

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