error-detection-q1
Both invoice numbers match exactly, character for character.
This is untimed educational practice for one cognitive skill. It is not a clinical, diagnostic, employment, or professionally recognized assessment, and it does not produce an IQ score or credential.
Both invoice numbers match exactly, character for character.
Both dates are written identically.
The first names differ: 'Jonathan' vs 'Jonathon'.
Both entries contain the same characters, but 42 has become 24 in the middle block: a transposition, which is the commonest copying slip. Comparing digit positions rather than reading the code as a whole is what exposes it.
Halstead has lost its second 'a' and become Halsted. Unfamiliar proper nouns have to be read letter by letter rather than by their overall shape, or single dropped characters slip through.
The order numbers agree and so does the day; only the month differs, 03 against 08. Splitting a date into its parts before comparing keeps a single changed digit from passing unnoticed.
Only one copy keeps every block intact; the others change the final letter, swap the first two letters, and transpose the middle digits. Checking block by block (letters, digits, letters) is faster and safer than reading the whole string at once.
Both figures use the same digits and the same decimal placement, but 45 has become 54. Transposed digits change a value without changing its length, so counting characters will never catch them.
The two strings agree up to the seventh character, but one continues with a further 0 and so runs one character longer. Comparing lengths first is the quickest way to find an inserted or dropped character.
Flat 2B and Wentworth Road both agree, but the house number has changed from 118 to 181. Numbers built from repeated digits are the easiest to misread, so compare them one position at a time.
The mismatched account number ends '...043' instead of the reference's '...034', the last two digits are transposed.
Every other code uses the 'PC-' prefix; 'PD-500' breaks the pattern.
Only one copy keeps all three blocks: the letters TL, the digits 3390 and the letters KD. The others turn D into O, transpose 39 into 93, and replace the letter L with a capital I, substitutions that all survive a quick glance.
A consecutive run from 4471 gives 4471, 4472, 4473, 4474, so the third entry should read 4473 rather than 4437. Testing a series against the sequence it is meant to follow turns a hard comparison into an easy one.
One address ends its domain with 'medlim' rather than 'medlin'. Letters built from the same strokes (n against m, or rn against m) are the hardest substitutions to see, so read a domain one character at a time.
One entry opens with the digit 8 in place of the letter B, so its prefix reads G8. When a rule concerns a prefix, read only the opening characters of every entry in a single pass rather than the whole code.
Counting characters gives 8, 8, 8 and 7, so one reference is a character short. Where a rule is about length, count rather than compare, the eye judges string length very poorly.
Weekly dates rise in steps of seven, so a run ending 11, 18, 25 must begin on the 4th; the list opens on the 3rd instead. Testing a series against the step it should follow is easier than comparing its entries with one another.
Three lines give whole counts, while one gives 3.5, which is not a whole number and so fails the stated format. Checking the shape of an entry is a separate task from asking whether its value looks plausible.
240 mm, 0.24 m and 24 cm are three ways of writing the same length, while 2.4 mm is a hundredth of it. Converting every value into a single unit before comparing is what makes a stray decimal point visible.
The quantities match (120), but the weights differ: 45.6kg vs 46.5kg.
Name, date and table number all agree; only the party size differs, 4 against 6. Comparing records field by field, in the same order each time, stops one changed value hiding among matching ones.
Quantity, unit price and item description all match, but the order asks for 3 m while the invoice supplies 2 m. A specification buried inside a description is as much a checkable field as the numbers beside it.
The four daily figures are identical in both records and add to 30.5, so the payroll total of 31.0 is the entry at fault. Recomputing a total from its parts is the only way to decide which of two disagreeing totals to trust.
Box count and destination agree, while the pallet count does not: 2 against 3. Naming the disagreeing field precisely turns a vague sense that something is wrong into a query someone can actually answer.
Both records use the same three numbers and the same year, but 04/11 has become 11/04, so day and month have exchanged places. Dates written under different conventions produce this error whenever the day is 12 or lower, because both readings look valid.
480 plus 96 comes to 576, which is what the quotation shows, so the invoice total of 567 has two digits transposed. Adding the components yourself is what decides which of two conflicting totals is right.
A 24-month term beginning on 1 April 2026 runs to 31 March 2028, but the summary closes it a year early. Where a record states both a duration and an end point, derive one from the other rather than reading each on its own.
Country code and middle block are identical, while the final block reads 0461 in one record and 0416 in the other. Splitting a long number into the blocks it is written in reduces one hard comparison to three easy ones.
Opening plus receipts minus issues gives 120 + 45 − 60 = 105, so a closing figure of 115 cannot follow from the other three. Rebuilding a balance from its movements is the standard way to locate the entry at fault.
Committee doubles the m as well as the t and the e, but the sentence gives only one m. Words carrying several doubled letters repay checking one pair at a time.
Occurrence doubles both the c and the r and ends in -ence. The r doubles because the stress in occur falls on the final syllable, which is the general rule when a suffix is added.
The sentence needs affect, the verb meaning to influence; effect as a verb means to bring something about, which is not what rules do to departments. A spellchecker accepts both, so this class of error survives every automatic check.
Separate carries an a in the middle, from the Latin parare, although it is very often written with an e. Learning the root of a troublesome word is far more reliable than sounding it out.
Maintenance ends in -ance rather than -ence. Unstressed vowels in the middle of long words give no clue in speech, so they have to be learned or looked up rather than heard.
One sentence repeats the word 'the'. Doubled short words are easy to read straight past, because the eye takes in a phrase as a unit rather than word by word.
The notice needs wear, the verb for putting on a badge, not where, which asks about a place. Homophones are spelled correctly in themselves, so only reading for meaning will catch them.
Accommodation doubles both the c and the m. Where a word can double two different letters, test each pair separately instead of judging the word by its overall look.
Thoroughly keeps its o after the r; throughly is a different word and no longer in ordinary use. Misspellings that differ from a common word by a single letter are the hardest of all to see.
One sentence writes receive with its vowels reversed, and after a c the e comes first. Attention tends to be drawn to the longer words in a sentence, which is exactly where the error is not.
A single company owns the logo, so the apostrophe belongs before the s. Deciding how many owners there are, before placing the mark, settles almost every apostrophe question.
The subject is 'each', which is singular, so the verb must be has; the plural noun sits inside a phrase that describes the subject rather than being it. Stripping the phrase out leaves 'each has signed', which settles the choice.
Two statements that could each stand alone need a full stop, a semicolon or a joining word between them, not just a comma. Testing whether each half works as its own sentence is what exposes the splice.
A plural that already ends in s takes the apostrophe after the s and adds nothing further. Placing the mark before the s would change the meaning to a single owner.
It's is only ever short for 'it is' or 'it has', while its shows possession and takes no apostrophe. Reading the sentence with 'it is' substituted shows at once which form belongs in each place.
An opening phrase describes whoever performs its action, so the subject that follows must be that person. Here it is the report, which cannot review anything. Ask who is doing the opening action, then read the next noun.
However joins two complete statements here, and a comma is too weak to hold them together. The same test applies as for any comma splice: could each half stand as a sentence on its own?
Both actions belong to the same past moment, so both verbs take the past form. Reading a sentence for its verbs alone makes an unintended shift of tense stand out.
A semicolon joins two statements that could each stand alone, and no joining word is needed after it. Anything that cannot stand as a sentence belongs after a comma instead.
With neither and nor, the verb agrees with whichever subject stands nearer to it, and 'delivery notes' is plural. Reading only the nearer subject together with the verb decides the form.
Adding the three prices gives exactly £14.85, so the receipt agrees with its own lines. Checking a total is a separate task from checking the individual prices, and both are worth doing.
Six units at £12.50 come to £75.00, so the stated line total falls £5 short. Where a line gives quantity, price and total, recompute the total first. It is the figure most often keyed by hand.
The four figures add to 800, so a stated total of 810 overstates the column by 10. Adding in convenient pairs, 145 + 95 = 240 and 260 + 300 = 560, makes the recount quicker and less error-prone than working straight down.
Fifteen per cent of £240 is £36, leaving £204; the invoice has deducted only ten per cent. Working a percentage out in parts (ten per cent is £24, half of that is £12) keeps the check quick and mental.
The three lines add to £17,525, which matches the stated grand total exactly. A check that comes back clean is still a result, so resist the pull to keep hunting for an error that is not there.
Work each line before adding: 3 × 24 = 72, 5 × 12 = 60 and 2 × 30 = 60, which come to 192. The stated figure is short by exactly 12, the size of one box that has been left out.
45 out of 300 is the same proportion as 15 out of 100, which is 15 per cent. Reducing the fraction to a denominator of 100 avoids a division and makes the check easy to do in your head.
Working through the movements gives 380, then 445, then 355, so the stated close of 335 is 20 too low. Carrying each intermediate figure forward, rather than combining all the movements at once, shows where a running balance goes astray.
Two kilograms cost £12 and the remaining half kilogram costs £3, giving £15. Splitting a quantity into a whole part and a remainder is a quick way to check a multiplication that involves a decimal.
Four nights come to £356 and 320 miles at 45p come to £144, and those two figures together make exactly £500. Checking each component separately before adding them is what lets you call a total right rather than merely plausible.
April has only thirty days, so a thirty-first cannot exist, whereas 2024 was a leap year and 29 February was real. Checking a date against the length of its own month is a validity test that the format alone cannot provide.
One entry supplies only three digits after the hyphen, so it breaks the pattern even though it has the same general shape as the rest. Reading a rule as a checklist of parts (letters, separator, digit count) makes each part separately testable.
A domain cannot carry two dots in a row with nothing between them, which is what one address does. Hyphens are permitted in both the local part and the domain, so they are not the fault here.
A share above one hundred per cent cannot be a part of a whole, while zero sits inside the permitted range and simply means none. Range checks catch the errors that format checks let through.
The 24-hour clock runs from 00:00 to 23:59, so any entry whose hour reads 24 falls outside it; midnight is written 00:00. Testing the first pair of digits against its permitted range is the whole of the check.
One entry gives the number as a word, which is not a numeric value however clearly it reads. Systems check the type of an entry before its value, and a word fails at that first step.
One filename puts the month before the year, reversing the order the rule sets out. Naming rules are checked by reading each element in turn, not by confirming that all the right pieces appear somewhere.
One entry gives only two letters after the space, with no leading digit, and has absorbed that digit into the outward part instead. Postcodes are easiest to validate by testing the block on each side of the space separately.
Recording an absent value as zero turns 'we do not know' into 'we measured none', which will distort every later total and average. Keeping missing data distinct from genuine zeros is a basic safeguard in any record.
Identifiers that begin with zeros lose them as soon as they are treated as numbers rather than text, which is why one reference appears in two forms. Storing codes as text preserves every character, including those that carry no arithmetic value.
A consecutive series with 3303 absent means that invoice has not reached the file, not that the others are wrong. Gaps are evidence about what is missing, which is the whole reason sequential numbering is used.
Reading only the initials gives A, B, C, D, E, C, so the final name should sit third, before Dunn. Checking the first letters of a sorted list is enough to find most ordering faults without reading the entries in full.
Two steps carry the number 3, so anyone told to return to step 3 has no way of knowing which is meant. Duplicated identifiers cause different trouble from missing ones, and both are found by reading the numbers on their own.
Adding 7 each time gives 14, 21, 28, 35, 42, so the fourth term is one short. Checking the difference between neighbouring terms turns a pattern question into simple subtraction.
The simplest explanation for a break in a printed sequence is an absent page, and it can be confirmed by seeing whether the text runs on across the gap. Test the simplest explanation before assuming a deeper fault.
Reading the values in order gives 4.50, 14.50, 4.95, 4.99, 15.00, so one large price has been dropped in among the small ones. This is the signature of a list sorted as text, where anything beginning with 1 comes before anything beginning with 4.
Successive 45-minute sessions run 09:00, 09:45, 10:30, 11:15 and 12:00, so the fourth start is a quarter of an hour early. Rebuilding a schedule from its stated interval is quicker than measuring each gap in turn.
Version 1.20 is a later release than 1.3, but it has been slotted in as though its number were text following '1.2'. Version numbers are compared part by part as numbers, which is why 20 outranks 3.
The multiples of seven run 7, 14, 21, 28, 35, so a review line at row 27 sits one row early. Where a rule states an interval, generate the expected values and compare, rather than measuring each gap separately.
The run is regular until the final gap, which is twice the stated interval, so the 11:15 reading has not been recorded. A doubled gap in an otherwise regular series points to an omission rather than a mistimed entry.
Two hundred units at £3.10 come to £620, so the invoice falls £10 short of the agreed terms. Checking three documents against one another means recomputing the figure they should share, not merely reading each one in turn.
The requirement is not two signatures but two directors, and only one signatory holds that office. Reading a requirement for the exact role it names, rather than for the count alone, is what makes the check bite.
Two weeks after 28 February is 14 March, which matches the advert, leaving the portal's 4 March standing alone with its leading 1 lost. Where three sources disagree, the one that can be derived from a stated rule usually settles which is right.
Thirty days from 3 June falls on 3 July, so nothing could be overdue two days earlier. Checking a claim about lateness means recomputing the deadline from the agreed term rather than accepting the reminder's own arithmetic.
'Up to 12 hours' states a ceiling, while eight hours describes a stated pattern of use, so both figures can be true at once. Before recording a contradiction, check whether the two figures were measured under the same conditions.
Only two options were approved, yet three appear in the tasks, so work has been created without a decision behind it. Comparing a decision with what follows from it is a different check from comparing two copies of the same text.
Twenty-six staff split into groups of eight need four supervisors, because three cover only twenty-four. A ratio written as 'one per eight' always rounds upwards whenever the division leaves a remainder.
A value can be perfectly valid and still sit in the wrong field, which no format check will ever detect. Confirming that a label means the same thing on both documents matters as much as checking the value beneath it.
A claim about every region fails the moment a single region did not rise, and the East was flat. Testing a universal claim means looking for one counter-example, not weighing up the overall picture.
The log records a specific dated event in March, so a claim of coverage from January cannot be supported for those two months. When a general claim meets a dated record, the dated record is the stronger evidence.
One event following another does not establish that the first caused the second; a seasonal peak or a price change would account for it equally well. Look for a rival explanation before accepting any causal claim.
Handling and settling affect the bottom of a crate differently from the top, so a top-only sample says nothing dependable about the rest. A sampling method is sound only if every part of the batch could have been selected.
Once the meter is reset the original value has gone, so the check that would catch a failed save happens too late to be any use. A verification step belongs before any action that destroys what is being verified.
The first statement rules out accredited suppliers failing, but says nothing at all about who else might pass. Reversing a conditional in this way is among the commonest faults in written reasoning.
A total is far larger than any single value, so including it roughly doubles the sum being averaged and pulls the result upwards. Checking which cells a formula actually covers is part of checking the number it produces.
The people most likely to be dissatisfied are the ones who left and so never saw the survey, which pushes the result upwards. Ask who could not have been included before generalising from any sample.
Self-review reproduces whatever misreading produced the error in the first place, so it detects far less than a second pair of eyes. Separating the doing from the checking is the entire point of a sign-off.
A single environment can hide missing settings, files or versions that only appear elsewhere, so a pass there is weak evidence about anywhere else. State the conditions a result depends on before extending it to other cases.
Moving from four complaints to two is a change of two, well within week-to-week variation, yet it reads as a halving. Percentages need their underlying counts printed alongside them before they can be interpreted.
A rule that suits a date of birth is wrong for a planned delivery, because the two fields permit opposite ranges. Checking that a rule matches the meaning of its field matters as much as checking that the rule runs.