Knowledge Base

Independent Variables

What Are Independent Variables

Independent variables are assumed to remain constant within observations but may differ between observations. To open the Independent Variables list, choose Setup > Independent Variables, or click Independent Variables in the Project Explorer.

Types Of Independent Variables

• User-Defined Variables – Variables that describe the subjects, observation sessions and environmental conditions. Examples include the name of the subject, the name of the observer, and the weather during the observation.
• Video Files – Name and location of the video files used in the observation. They are added automatically to the independent variable list when you create an observation. The scope of a video file is always observation. If you already have observations, click Add Video to add video files to your observation.
• Audio Files – Name and location of the audio files used in the observation. The scope of an audio file is always observation. If you already have observations, click Add Audio to add audio files to your observation.
• External Data Files – This column is only present when you have the External Data Module. It shows the name of the external (physiological) data files imported into an observation. The scope of an external data file is always observation.
• System Variables – Three variables are automatically created by the system: the start time, stop time and the duration of an observation. To change the format of these variables, click the arrow in the Format field and make your selection in the window that appears.

Create User-Defined Variables

Aim

• To define variables that potentially influence the value of a dependent variable.
• To list the names or numbers of the subjects in your observations.

Prerequisite

The Independent Variables list is open. If this is not the case, choose Setup > Independent Variables.

Procedure

1. Click Add Variable.
2. Enter the following options: variable type, variable format, predefined variable values (optional), variable scope, and value update.

Notes

• You can add maximally 40 user-defined variables.
• The independent variable name may have maximally 64 characters. The description may have maximally 255 characters.

Variable Type

Click the arrow in the Type field and choose one of the following options:

• Text – A text variable is denoted by alphanumeric characters, composed of letters, numbers or both. For example, the name of the observer.
• Numerical – A variable represented by numbers only, for example, the age of the subject.
• Timestamp – A variable represented by a time stamp, for example the starting date and time of the experiment.
• Duration – A variable represented by a duration, for example, the duration of the treatment.
• Boolean – A variable that is either False or True. For example, the presence of the observer during the test.

Variable Format

• Text And Boolean Variables – For Text and Boolean variables you cannot specify a format.
• Numerical Variables – Choose the number of decimals (maximum 9). Deselecting No. of Decimals will result in using integers. Select Scientific Notation to display numbers as, for example, 1.485e+0.03 instead of 1485.236. In the Unit field, enter the unit of your variable, for instance, years for the age of the subject.
• Timestamp Variables – Specify the format. The format f represents the decimals you specified in the Time Formats tab of the Project Settings window.
• Duration Variables – Specify the format. The format f represents the decimals you specified in the Time Formats tab of the Project Settings window.

Note On Regional Settings

The program uses the decimal separator specified in your computer's regional settings (Control Panel > Region). If you change regional settings, close and restart The Observer XT.

Predefined Variable Values

Optionally predefine values so you can select from them when entering user-defined variables. For Timestamp and Duration variables you cannot specify predefined values.

• Text Variables – Enter the text you want to choose from. Select Allow Other Values if you are not sure whether the values you have defined are exhaustive. This allows you to add new values as they are needed.
• Numerical Variables – Choose whether your variable can have any value, a value in a range, or predefine values. Select Allow Other Values if you are not sure whether the predefined values are exhaustive, so you can add new values when needed.
• Boolean Variables – Enter the names to display. For instance, if your variable is Parent Present, you may define the values No (False) and Yes (True).