Introduction
The Problem
Categorical or nominal variable sets that permit multiple responses (i.e., multi-punch, multi, multiple response questions) are displaying in a table so that there is one row for each response containing the variable's label, and each code is appearing as a column. Or, to use different terminology, the multiple response data has been created in the data file with a max-multi structure.
Method
The easy solution
The Structure for such variable sets needs to be set as Binary - Multi (Compact) (this is the correct structure in data for multiple response data that has been set up with max-multi coding).
The better solution
The reason that Displayr fails to automatically detect the structure of such data is because it is ambiguous. It is not possible to determine with complete confidence whether it is a grid (or, to use the Displayr terminology, Nominal - Multi), or a Binary - Multi (Compact), so it defaults to Nominal - Multi as this is much more common.
In most situations, the best solution is to have the data file exported so that each code is represented by a separate binary variable. This is superior to using the max-multi format in a number of ways:
- Displayr will be able to automatically determine the correct Structure.
- Where there are missing values, the percentages will be correct. That is, the main reason why max-multi coding is, in general, a bad idea is that if different respondents were shown different options, there is no way that this can be deduced from the data (i.e., where the data is setup as binary variables, a missing value means that an option was not shown, whereas with max-multi it can either mean the option was not shown or that it was not selected).
- Most multivariate tools conduct their analysis using individual variables rather than variable sets (i.e., although you select variable sets when running the analysis, the math is done using variables). For this reason, some of the multivariate methods in Displayr do not let you select Binary - Multi (Compact) data, because of the risk that the user will not appreciate that the way that the data is stored will change their outputs. If you need to do multivariate analyses but have data in the max-multi format, select the variable set in the Data Sets tree, click the Plus (+) that appears when you hover over it > Ready-Made New Variables > Binary Variable(s). This will then create a new Binary - Multi variable set.
The special case of large code frames
Max-multi can be used in any situation where it is known with certainty that the same code frame applies to all respondents (e.g., coding of most open-ended questions). Where this is the case and there is a very large code frame (e.g., 6,000 models of car), it will generally be superior, as the resulting data file will be smaller, the analyses will compute faster and there will be less chance of out-of-memory browser issues.