Error Checking: The Attention-to-Detail Test That Separates Accuracy From Speed
Error checking is the fastest-paced section in any aptitude test. On the Thomas GIA, you have 90 seconds to attempt 40 perception items. Aon cut-e is similar. This section does not reward intelligence in the usual sense. It rewards a specific kind of disciplined looking: visual scanning that is fast enough to finish and careful enough to catch small differences. Most candidates have never trained this skill deliberately, which is exactly why deliberate training produces large gains.
What error checking actually measures
Error checking measures visual perception speed and accuracy. The test presents pairs or groups of strings, numbers, or records and asks you to find the mismatch. Simple format, hard execution under time pressure. The underlying skill correlates with attention-to-detail roles: data entry, quality assurance, accounting, and clerical work.
The catch is that the test punishes both inaccuracy (miscounts) and excessive caution (running out of time). Speed and accuracy are both scored. Candidates who try to be careful lose points by not finishing. Candidates who rush lose points by flagging the wrong differences. The scoring sweet spot is completing about 80 percent of the items with 90+ percent accuracy.
Error checking is most common on tests for clerical, administrative, and technical operations roles. Thomas GIA uses it in the Perceptual Speed section. Aon cut-e uses it in the adept Scales e3 and scales ix modules. Some SHL variants use it in accuracy-focused assessments. It is rare on general cognitive tests like the CCAT or Wonderlic.
The three error-checking formats
Each tests a slightly different perceptual skill. Format drives strategy.
Spot the difference
Two strings or records are shown side by side. You mark whether they match or not. The mismatch is usually one character: a transposed digit, a different letter, or a missing punctuation mark. Fastest format.
Match from multiple
A reference item is shown, then 4 to 5 candidates. You pick the one that matches. Slower because you compare each candidate against the reference, not against each other.
Find the error in a record
A longer record (a row in a table, an address, a product listing) is shown, and you mark whether any field contains an error or which field does. The skill is scanning through multiple fields under a single time budget.
Worked examples
Three hand-crafted error checking questions with full walkthroughs. Do them with a timer first. Then read the solution.
Compare character by character.
AX4592 matches AX4592.
First hyphen matches.
Next segment: PQB vs PBQ. The letters Q and B are transposed.
Mark DIFFER.
The trap is scanning by overall length or by the last segment (00137 matches in both). Transpositions are the most common intentional difference on error-checking tests because they are the hardest to spot.
Compare each candidate against the reference.
Option A: C12-AP-5520-9871. Matches exactly.
Option B: C12-AP-5520-9817. Last two digits transposed (71 to 17).
Option C: C12-AP-5502-9871. Middle segment has digits transposed (5520 to 5502).
Option D: C12-PA-5520-9871. Second segment has letters transposed (AP to PA).
Only option A matches.
The trap is scanning too quickly and picking option B or D (which differ only in transposed pairs at different positions). Always scan the full string end to end, not just the first 3 characters.
Compare each field end to end.
Name: Johnson, R. = Johnson, R. Matches.
Age: 34 = 34. Matches.
ID: 88291-A = 88291-A. Matches.
City: Manchester vs Machester. Missing "n" in the entry. Error found.
Mark "Error in City."
The trap is scanning short fields (Name, Age, ID) thoroughly and then glossing over the longest field (City) in a hurry. Errors are more likely to be planted in longer fields because they are harder to spot. Always give longer fields equal attention despite the time pressure.
Tests that use error checking
Error checking is narrow in scope but heavily weighted on tests for clerical, accounting, quality assurance, and technical operations roles.
Thomas GIA Perceptual Speed section uses error checking with 40 items in 90 seconds.
Aon cut-e uses error checking as a core perception module, often paired with other cognitive sections.
Specialized for accuracy-focused roles; extended error-checking with multiple-choice comparisons.
Used for administrative and data entry roles.
Three error checking mistakes
Scanning by shape, not by character
Reading at normal reading speed causes the brain to pattern-match on word shape, missing single-character differences. Error checking requires letter-by-letter scanning, which feels slower but is actually more accurate.
Skipping the final segment
Candidates run out of time and often rush the last 10 items, which lowers accuracy. Budget time so the final items get the same attention as the first. Skip rather than rush when time runs short.
Not using a visual anchor
When comparing two long strings, put a finger or cursor on each and move them together. This prevents your eye from jumping around and missing a character. On paper tests, a ruler or finger works. On computer tests, the cursor works.
A 7-day error checking plan
Days 1 to 2: Speed diagnostic
Take 40 error checking items untimed, then 40 timed at 2 seconds each. The gap shows how much accuracy drops under time pressure.
Days 3 to 4: Character-by-character scanning drills
Practice 100 string comparisons per day. Use a visual anchor (finger, cursor, ruler). Focus on accuracy first, speed second.
Days 5 to 6: Timed sets
Add time pressure. Target 90 percent accuracy at 2 seconds per item. Slow down if accuracy drops, speed up only when accuracy is stable.
Day 7: Full mock and rest
One full-length error checking section at test pace. Then no more prep. Sleep 8 hours before test day.
Related reading
Error Checking FAQs
Error checking rewards disciplined looking. Train the habit.
Full-length, timed error checking practice modeled on Thomas GIA and Aon cut-e formats.
Start Error Checking Practice