6.4 Exact-Duplicate Comparison & Detail Checking

6.4 Exact-Duplicate Comparison & Detail Checking

FPSI's sample Reasoning/Analyzing section includes items that list pairs of codes, such as license plates, case numbers, or serial numbers, and ask: "How many of the items listed below are EXACT duplicates of one another?" The answer choices are counts: none, one, two, or three. These items measure perceptual accuracy, the ability to compare two strings character by character without letting the brain "autocorrect" a difference. It is a job skill: a plate run with one wrong character returns a different vehicle, and a serial number copied with a transposed digit hides a stolen item.

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What the Item Looks Like

Here is an original example in the same style:

4471                 4471
B83K92M              B83K29M
7720QT19             7720OT19
A55-901-RX           A55-901-RX
30918LN6             30918LM6

Compare each pair:

1. 4471 / 4471: identical. Duplicate.
2. B83K92M / B83K29M: the 9 and 2 are swapped. Not a duplicate.
3. 7720QT19 / 7720OT19: the letter Q became the letter O. Not a duplicate.
4. A55-901-RX / A55-901-RX: identical, including the hyphens. Duplicate.
5. 30918LN6 / 30918LM6: the N became an M. Not a duplicate.

Two pairs are exact duplicates, so the answer is two. Notice that "none" is a legitimate answer; do not assume at least one pair must match.

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Why Careful Readers Still Miss Differences

Skilled readers recognize words by their overall shape and fill in details from expectation, which is why a typo in a familiar word often goes unnoticed. Codes have no meaning to anchor them, but the same shortcut still operates: after seeing "B83K9" the eye expects the pattern to continue and skims the last two characters. The fix is to deny your brain the shortcut by checking a few characters at a time and pausing on any character that has a look-alike twin.

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The Differences Test Writers Use

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A Reliable Comparison Method

1. Compare lengths first. If one string has more characters than the other, it is not a duplicate. Counting takes two seconds and catches dropped or added characters.
2. Chunk each string. Break it into groups of three or four characters (B83 K92 M) and compare chunk by chunk rather than as one long blur.
3. Compare in the same direction every time, left to right, and say each character silently ("B, eight, three, K, nine, two, M").
4. Mark each pair immediately. Where scratch paper is allowed, write a check or an X for each pair as you finish it rather than keeping a running count in your head. Where it is not, finish one pair completely before moving on and recount before answering.
5. Count the checks, then match the count to the options. Recount once before you mark the answer.

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Paper Versus Screen

On a paper test, slide the edge of your answer sheet or a finger down the list so only one pair is visible at a time, and touch each chunk with your pencil tip as you compare it. On a proctored online test, FPSI's instructions allow scratch paper for specific sections only, and you cannot write on the screen. Where scratch paper is allowed, write each pair number with a check or X as you finish it. Where it is not, keep your place with the mouse pointer, finish each pair completely before looking at the next, and recount the matches once before answering. Zooming in with the browser is not something to count on, so practice comparing strings at normal size.

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Speed Versus Accuracy

Duplicate items are fast points, but one missed difference changes the count and makes the whole item wrong. A sensible budget is about a minute for a list of five or six pairs. Because the PACT allows about 108 seconds per item on average in a 3-hour session, a careful minute here is affordable. If you finish a list and feel unsure about one pair, re-check only that pair rather than the whole list.

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Building the Skill Before Test Day

Perceptual accuracy improves with short, frequent practice:

• Make your own lists. Copy ten license plates or product serial numbers, then write a second column in which you change three of them in one of the ways in the table. Swap lists with a study partner and time each other.
• Practice with mixed strings. Include letters, digits, and hyphens, because mixed strings are where look-alike substitutions hide.
• Check your errors. When you miss a difference, note its type. Most people miss one type more than the others, and knowing yours tells you where to slow down.
• Keep sessions short. Five minutes a day for two weeks builds more accuracy than one long session, because the skill depends on sustained attention.