Knowledge Base

The Statistics Result Table Does Not Appear

Problem: The results table in Trial Statistics or Group Statistics and Charts shows no headers and no results.

Explanation/Solution: This could happen for example when:

• The experiment has no data yet.
• The data have been completely filtered out in the Data Profile. Please check your data selection.
• For Group Statistics: An independent variable was inserted in the table Layout, and at least one of those groups contains multiple values of that variable.

Example: In the Data Profile, you group tracks in two groups, Treated and Control. In the Group Statistics and Charts, you insert the independent variable Rat ID in the Layout, but each group contains many values of this variable (one per subject tested). Therefore, the grouped results cannot be listed properly.

To solve this, either remove the variable from the Layout (Modify the layout of the results table), or in the Data Profile group your trials in a different way. See also Trial Statistics Result.

The Data Preparation Report Says "Failed" for Some Trials

This message occurs in experiments with Deep Learning based body point detection. In some cases EthoVision XT fails to review the tracks and fix subject identity swaps. For example, when the two subjects spent most of the trial time in close contact, or the video file was too short to obtain a reliable trained neural network. See a note in Prepare the Data in Multi-Subject Trials.

Time in the Arena

Problem: "Subject not found" gives one value (e.g. 5%) and the total time the animal is in the arena (Cumulative duration% in the Arena) is 96%, while I expect them to be complementary.

Explanation/Solution: In the following example there is a gap of 25 frames of "subject not found". With 25 frames per second (so 0.04 s per frame), that comes down to a missed sample time of 1 second, which may be for example 0.5% of the total time. That percentage you see in the Trial List. However, when the subject goes missing, EthoVision XT assumes that it is still in the arena in the next 3 frames, before considering it "not in the arena". In this example, the gap is not 25 frames but 25-3 = 22 frames. Therefore, the total time "not in the arena" is 22*0.04 s = 0.88 s instead of 1 s. Thus, Subject Not Found and Cumulative Duration% in Arena do not always match.

The Results Table Contains "?" in Many Cells

This could indicate that one or more trials are corrupt. However, it is also possible that you edited the tracks and something went wrong with editing.

1. Click Calculate and take note of a trial that gives the "?" results.
2. Go to the Track Editor, select the trial and then click Undo All. Note that this action erases all your edits in that trial.
3. Re-do editing when necessary.
4. Run analysis.

The Time That I Started Tracking

This applies to cases when you positioned the video later than its starting point and then clicked Start Trial.

1. Export the raw data (choose Analysis > Export > Raw Data).
2. Open the exported file and look at the difference between the value next to Start Time and the value next to Video Start Time.

I Get More Zone Entries Than Expected

This applies to In Zone variables where the number of entries is higher than expected. This could occur for different reasons:

• A common issue is that the center point of the subject moves back and forth around the boundary between zones when the animal moves just on that spot. This overestimates the number of true zone entries. To avoid this, use the Zone Exit Threshold in the In Zone dependent variable settings, or use all three body points to score a zone entry. See In Zone.
• Another reason for an overestimate of zone entries is that the center point is no longer detected in a zone, although the subject is still found. Consider for example a zero maze where the open and closed zones do not cover the arena completely. The region of the arena outside the zones means that when the center point is detected there, a zone exit is scored. A new zone entry is scored when the center point is found in the zone again, resulting in a train of repeated zone entries.

To solve this issue, re-draw the zones in such a way that they overlap the entire region of interest within the arena.

The Analysis Profile Does Not List Mobility and Head Direction

This occurs when your experiment is set to Number of Subjects = 2 and Body Point Detection Technique = Deep Learning. In that case the software does not calculate the body contour and the Head Direction line.

Source: EthoVision XT 19 Help, Noldus Information Technology