Concept: Variable

A Variable is a memory space where a piece of information can be stored. Variables have a name (or identifier) that can be used to access the information stored, and are attached to an object in TAO, for example an item in a test. Various different types of information are stored in TAO variables, the most important of which (for this course) is its value, which is assigned during one of the processing steps that will be described later.

There are two kinds of variable used in TAO: Response Variables and Outcome Variables. Declarations are used to declare the information these variables contain. These declarations will be discussed in more detail after the lessons on variables.

Response Variable

A Response Variable is a variable used to store the raw response of the test taker - the answer the test-taker has given to a specific test question. The TAO Glossary defines Response Variables as "Variables bound to an Item which record the candidate's Responses. Their properties are defined by Response declarations".

In other words, they are attached to the items in which they are declared and can only be used at the item level. One of the properties they can have is 'Correct Response', in which the desired answer to the interaction in the corresponding item can be stored. For the first item in George's assessment about the capital of Myanmar, the property 'Correct Response' will be 'Naypyitaw', as you can see in the example below.

Outcome Variable

An Outcome Variable is a variable in which a computed value is stored - either a score or any other value. The TAO Glossary defines Outcome Variables as "Variables which store Outcomes. Their properties are defined by outcome declarations. Values are set either from a default given within the declaration or by a response rule encountered during Response Processing (for Item outcomes) or Outcome Processing (for Test Outcomes)". 

In other words, they are used to store information which has been computed during the processing of a finished assessment. Outcome Variables can be attached to an item or to the whole test, and are used at both the item level and the test level. One property they can have is 'Interpretation', in which an explanation of the value which is to be assigned is stored.

Below is an example of an Outcome Variable computed for the first item in George's assessment about the capital of Myanmar.

As you can see, the values in these examples have not yet been assigned to the variables - that comes later.