How Army Error Detection works
Two strings appear, one above the other: the original and a copy. They mix letters, digits and symbols, and the copy may or may not contain mistakes.
You study both, then press Next Step. The strings disappear and five buttons appear, 0, 1, 2, 3 and 4, for the number of mistakes in the copy. So you count while the strings are on screen and carry only the total across.
The section is timed as a whole, not per item, and items keep coming until time runs out. Preparation sites put it at about 5 minutes and 40 items. Speed and accuracy both count, and the Army’s practice advice is to make your best guess and move on when an item seems too hard.
How to count the errors
Use one pass, left to right, on every item:
- Compare the two strings in blocks of three or four characters rather than one character at a time.
- Add one to a running tally for every position where the characters differ.
- Treat a swapped pair, such as 58 copied as 85, as two mistakes, because two positions are wrong.
- Watch the look-alikes: 0 and O, 1 and l, 5 and S, 8 and B.
- Press Next Step as soon as you reach the end. A second scan costs more time than the odd miss.
Worked example
The original reads JH58 3PW 14:20 and the copy reads JH85 3PV 14:20.
Block by block: JH matches. 58 has become 85, so two positions are wrong. 3P matches, then W has become V, a third mistake. 14:20 matches. Press Next Step and tap 3.
Tips for the real Error Detection section
- Try the Army’s free practice questions first. They show the real screens, you can repeat them as often as you like, and the Army gets no results from them.
- Expect 0 to be a real answer. A copy with no mistakes is not a trick.
- Find a rhythm. An Army answer on preparing says the test measures speed and accuracy, so a steady pace beats bursts and pauses.
- Do not wait for a countdown. Candidates report that sections end without warning.
- At the Assessment Centre the test is on a touch screen, so it may feel slightly different from practising with a mouse.
Practise Error Detection on CogniPrep
Our Error Detection drill runs for 5 minutes with no countdown on screen, gives you new items until the time is up, and hides both strings when you press Next, with no going back. Answers are marked with the guessing correction the old BARB used, right answers minus wrong answers divided by four, and you finish with a score out of 100 and an estimated GTI. The 5 minutes is a preparation site’s figure, because the Army does not publish one, and there are no practice items before the clock starts.