This code system http://hl7.org/fhir/variable-handling defines the following codes:

CodeDisplayDefinition
continuous continuous variableA continuous variable is one for which, within the limits the variable ranges, any value is possible (from STATO http://purl.obolibrary.org/obo/STATO_0000251).
dichotomous dichotomous variableA dichotomous variable is a categorical variable which is defined to have only 2 categories or possible values (from STATO http://purl.obolibrary.org/obo/STATO_0000090).
ordinal ordinal variableAn ordinal variable is a categorical variable where the discrete possible values are ordered or correspond to an implicit ranking (from STATO http://purl.obolibrary.org/obo/STATO_0000228).
polychotomous polychotomous variableA polychotomous variable is a categorical variable which is defined to have minimally 2 categories or possible values. (from STATO http://purl.obolibrary.org/obo/STATO_0000087). Suggestion to limit code use to situations when neither dichotomous nor ordinal variables apply.
<status value="active"/><experimental value="false"/><date value="2021-01-05T10:01:24+11:00"/><publisher value="HL7 (FHIR Project)"/><contact><telecom><system value="url"/><value value="http://hl7.org/fhir"/></telecom><telecom><system value="email"/><value value="fhir@lists.hl7.org"/></telecom></contact><description value="The handling of the variable in statistical analysis for exposures or outcomes (E.g. Dichotomous, Continuous, Descriptive)."/><jurisdiction><coding><system value="http://unstats.un.org/unsd/methods/m49/m49.htm"/><code value="001"/><display value="World"/></coding></jurisdiction><caseSensitive value="true"/><valueSet value="http://hl7.org/fhir/ValueSet/variable-handling"/><content value="complete"/><concept><code value="continuous"/><display value="continuous variable"/><definition value="A continuous variable is one for which, within the limits the variable ranges, any value is possible (from STATO http://purl.obolibrary.org/obo/STATO_0000251)."/></concept><concept><code value="dichotomous"/><display value="dichotomous variable"/><definition value="A dichotomous variable is a categorical variable which is defined to have only 2 categories or possible values (from STATO http://purl.obolibrary.org/obo/STATO_0000090)."/></concept><concept><code value="ordinal"/><display value="ordinal variable"/><definition value="An ordinal variable is a categorical variable where the discrete possible values are ordered or correspond to an implicit ranking (from STATO http://purl.obolibrary.org/obo/STATO_0000228)."/></concept><concept><code value="polychotomous"/><display value="polychotomous variable"/><definition value="A polychotomous variable is a categorical variable which is defined to have minimally 2 categories or possible values. (from STATO http://purl.obolibrary.org/obo/STATO_0000087). Suggestion to limit code use to situations when neither dichotomous nor ordinal variables apply."/></concept></CodeSystem>