Except for a few special exceptions, formulas work on numbers, not text fields.
However, you may want to specify a formula based on a checkbox group (e.g. a visibility formula based on a text field set to display as a checkbox group).
Perhaps you have a text field (Text1), set to display as a checkbox group, and the checkbox options are Yes and No. Below this checkbox group, you have another text field (Text2) that should be visible if the answer to Text1 is "Yes," but hidden when the answer to Text1 is "No."
In this scenario, the easiest way to specify the visibility formula on this field is to look at the length of the text field.
In the example above, Text1 has three possible values:
If Text2 is supposed to be visible only when the user has specified a value of "Yes" for Text1, then the visibility formula for Text2 should be: len(text1)=3 groups in Case Management records?