Knowledge Base

Offset And Lag

Offset is the estimated difference in time between the clocks that cumulated up to the time of the update. This is the accuracy of synchronization of the Stimulus Presentation Tool with FaceReader. A positive value means that the FaceReader PC clock is faster than the test PC.

Lag (also known as delay) is the traveling time of time packets from the client to the server and from the server back to the client. The shorter this lag, the more accurate the estimate of the offset between clocks.

1. You are now ready to start the test with the Stimulus Presentation Tool.

See Run A Test

Notes

• After clicking Update Now, always make sure that on the Network Time window the Status cell for the FaceReader PC says Good.
• To change the order of the servers in the NetTime Options window, copy and paste the name of one cell to the other.
• Click Update Now every time you start a test to keep the time offset between FaceReader and Stimulus Presentation Tool as low as possible.
• For more information:
  • https://en.wikipedia.org/wiki/Network_Time_Protocol
  • http://www.timesynctool.com

Event Markers

Event markers are used to indicate that, for instance, the participant was distracted or was trying food product A. With Event markers, you can mark the parts of the analyses you are especially interested in and that were not defined as Stimuli beforehand. In contrast to Stimuli, Event markers have no fixed duration. In FaceReader you can compare the analyses over these time periods with other data.

Main Topics

• Define Event Markers
• Score Event Markers

Define Event Markers

Aim

To specify the markers and their associated key codes.

Prerequisite

Your FaceReader license includes the Project Analysis Module.

Procedure

1. Choose Project > Event Marker and then Add Event Marker.
2. In the Name field, enter the Event marker name, for instance, Food product A.
3. Click the button on the right of the Trigger Key field and enter the key for this marker. This is the key on your keyboard that you press when the event (In this example Test participant takes food product A) starts.
4. Select a color for the marker and click OK. This color will be used throughout the program for the Event marker.

Notes

To delete or edit an Event marker:

1. Open the Event Markers tab at the bottom of the Project Explorer.
2. Right-click the Event marker you want to delete or edit and select the option you require.

Source: FaceReader 10 Reference Manual (Help), Noldus Information Technology