True OMR
Second Darkest Mark Detection
For
Erasure Analysis
Mark Sense (Generic Image Scanners) True OMR (Scantron)
Identifies mark from black and white
(bitone) image
True OMR sees marks in grayscale
Allows for Plain Paper Printing
Allows for Plain Paper Printing
Marks are either Black (present) or
White (absent) based on a single
threshold.
Darkness of the marks is used to
intelligently and accurately distinguish an
erasure from an intended mark (mark
discrimination).
Many erasures will read as jet black
marks.
True OMR can accurately identify a
mark as being light, dark, or an erasure.
Useful for low stakes data collection,
such as surveys, where picking up some
erasures as marks does not significantly
affect the survey outcome.
Useful for all data collection when
accuracy matters.
Poor choice for most testing due to the
inability to determine darkest mark or
light marks. Close to 100% accuracy
can only be achieved with time
consuming manual verification of original
documents, which can introduce human
error.
True OMR is the standard for the highstakes testing industry with an accuracy
of 99.9997%, without manual
verification. If the results from a test are
important, shouldn’t they be accurate?
How Mark Sense Sees the World
• Black
and White only. No shades of gray.
• Loss of detail.
• Loss of accuracy when reading data
Mark Sense Black and White Image
Can you tell which are
the intended marks?
The answers will be
shown 2 slides from
now.
• Bitone. Only Black and White.
• Cannot tell the difference between an erasure and an intended mark.
• Mark Sense loss of detail causes multiple marks when erasures are intended.
• Mark Sense is a poor choice for high stakes testing.
Mark Sense Read
Bi-Tone
Original
Scanner Normal Threshold
Reads Bubble 5
Omit
Mark Sense Read
Bi-Tone
Original
Scanner Low Threshold
Multiple
Reads Bubble 3
How Mark Sense Sees the World
• Black
and White only. No shades of gray.
• Loss of detail.
• Loss of accuracy when reading data
How True OMR Sees the World
• Grayscale. Black, White, and various
shades of gray in between.
• Increase in detail.
• Increase in accuracy when reading data.
True OMR Grayscale
Correct Responses:
D
E
D
Mark Sense
OMR
Mark sense would have read: mult, C, mult, A, mult, for 3 wrong reads.
OMR would have read: D, C, E, A, D for 5 accurate reads.
• true OMR has 16 level grayscale read.
• true OMR can accurately tell the difference between an erasure and an intended
mark.
• true OMR’s increase in detail causes increase in read accuracy.
• true OMR is ideal for high stakes testing.
What About Light Marks?
Original Mark as
seen on sheet
Bitone Mark Sense
Reads as Omit
true OMR Reads a
Valid Mark
Marks that are light can be dropped out by bitone mark sense, and
considered to be omits. Because the image will not show light marks, the
actual student sheet must be retrieved for visual inspection and correction.
Because True OMR sees in grayscale, light marks will still be read as valid
marks, with no user verification required.
True OMR 16 Level Read
Mark Threshold (user adjustable)
[N]ormal
setting
[D]ark
[L]ight
setting
setting
0
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15
A B C D E F
Paper
* Every bubble on the form gets assigned a value from 0 through F (0 – 15)
True OMR 16 Level Read
Mark Discrimination Summary
If two or more valid marks are present:
• They must be 3 levels apart or a multiple is
recorded
• If both marks are at or above the
discrimination cutoff, then there was no
attempt at an erasure, and a multiple is
recorded.
Mark Threshold, Mark Discrimination, and Mark Discrimination Cutoff are all
user definable.
True OMR Second Darkest Mark Read
Returns up to 3 fields:
• Darkest Mark Field – D,B,C,D,E
• Second Darkest Mark – A, -,E, - ,B
• Optional Darkness Zone - 600E00F00000F08000C00600B
Formatted Output :
D,B,C,D,E,A,-,E,-,B,600E00F00000F08000C00600B,
Darkest
Marks
Second
Darkest
Marks
Darkness Zone information (optional)
Dashes indicate omits
Scantron’s real-time data recognition (True OMR) Generic
Image
allows for detection of error conditions during
Scanners
scanning
Skewed document - Can cause marks to be missed or misinterpreted
No
Missing critical data – Scanning can automatically stop if required data is
missing such as an ID number or a signature
No
Folded corners covering data – Ensures data under the fold isn’t missed
No
Multiple sheet feeds - Detects when 2 sheets stick together and are
scanned at the same time. Prevents loss of data – missing students
Sometimes
Scantron’s scanners are
engineered for data capture
applications
Generic Image
Scanners
Scantron scanners are engineered to read
consistently from scanner–to-scanner and form-toform.
Consistency generally not a
design priority.
Scantron scanners with printers are designed to be
interactive. They can print information like test
scores and error messages on a form based on
what was read from that form.
Printers are only available on
more costly models. Limited,
pre-determined information (if
any) like a sequence number
and or date. Not interactive error messages and test
scores cannot be printed on a
form.
Scantron can determine the second darkest mark.
Cannot determine darkest or
second darkest mark.
True OMR Verification
• Because true OMR can distinguish between an intended mark and
an erasure, and is capable of reading light marks as well, manual
verification of data is not required.
– Saves time
– Reduces the chances of human error
• True OMR can still be verified if desired.