A ComputedProperty produces the result of an Expression. An expression might be understood as a (complex) formula that returns a value. The result can be either a scalar (a single value) or an array (a composite of values). A scalar can be a number, a text, or a Boolean value (true or false).

To construct the formule within the expression of a ComputedProperty a number of predfined elements are available. These are:

PropertySomething that has a value, like a question, a computed property, or a declared property.
OperatorArithmetic operators (like: +, -, *, /, and logical operators (like: &&, <, >, || ). If you don't know exactly what a certain operator does, do not use it!
TextualValueA series of characters, like "Hello". TextualValues can be added (or rather: concatenated) with the '+'-operator. E.g. 'Hello' + ' world' = 'Hello world'
ReferenceValueA reference to another document, e.g. a questionnaire.
ExpressionAn expression is a combination of values, prpoperties, operators, and scripts that are interpreted (evaluated) and then produces (returns). As in mathematics, the expression is (or can be said to have) its evaluated value; the expression is a representation of that value.
IsUndefinedReturns the computed property as true or false depending on whether the referenced property has a valid value, i.e. ''is defined''.
Contains Contains is a logical operator that determines whether the referenced property contains a specified value. This especially refers to array properties, properties that carry more than one value. E.g. an array property x might have the value (2, 4, 5, 7). Than the expression x contains 4 would be true, whereas x contains 3 would be false.
NormtableLookupTransformation function that converts the key value (mostly a raw score) specified by a reference property, to the norm value derived from a specified NormTable.
SumProductA simple expression to calculate the weighted sum of a series of referenced properties, each with its own weigth.
ScriptA series of expressions in JavaScript. Very powerful tool. when using a script all other fields must be removed.
CountCounts all occurences of the referenced property only if they have a defined value. Relevant for group reports.
CountAllCounts all occurences of the referenced property whether they have a defined value or not.
MaximumReturns the maximum value of all occurences of the referenced property. Relevant for group reports.
MinimumReturns the minimum value of all occurences of the referenced property. Relevant for group reports.
AverageReturns avarage value of all occurences of the referenced property. Relevant for group reports.
StandardDeviationReturns standard deviation of all occurences of the referenced property (sample estimate, numerator= n-1). Relevant for group reports.