What is an OMR Threshold Level ?

OMR Threshold Level is the level of darkness (mark density) for a bubble to be evaluated as a mark.

The threshold level has a 16 point scale: 0 1 2 3 4 5 6 7 8 9 A B C D E F (X)

• 1 being the lowest readable darkness (mark density)
  • 0 being not readable
• F being the highest readable darkness (mark density)
  • anything above F, is X which is the highest

OMR confidence is calculated per OMR segment and per OMR field as an appropriately-computed averaged confidence of all positions in the segment or field, respectively.

For bubbles that are marked, the higher the mark density is above the Threshold level, the higher the confidence will be, thereby indicating a higher level of certainty that the bubble is marked. Whereas for unmarked bubbles, the further the mark density is below the Threshold level, the higher the confidence will be, thereby representing a higher level of certainty that the bubble is marked. Therefore, the confidence of unmarked bubbles decreases as the mark density approaches the Threshold Level, and confidence for marked bubbles increase as the mark density exceeds the Threshold Level.

Our Suggestion:

There is no preferred or standard threshold level; therefore we suggest that users test out their forms with different levels of marking density to determine your acceptable mark densities.

The lower the Threshold Level, the better the recognition engine will be able to identify marginally marked bubbles. However, raising this level enhances the recognition engine's ability to correctly identify unmarked positions (e.g. dirt, stray marks, poorly erased marks). If unmarked positions in an OMR field are being incorrectly identified as marked, raise the Threshold value a percent or two at a time until testing reflects accurate results.

To adjust the Threshold Level for your project:

1. 1. Open ‘TestAnyTime’
2. 2. Select ‘Utility’ then ‘Configure Scanner’
3. 3. Select ‘Scan Setting’ tab, then ‘Min Threshold’