We gave a pattern name to 2,453 wrong answers in our ACT English bank and grouped them.

Rule-based mechanics, the errors a grammar reference covers, account for 959 of them, or 39 percent. Another 1,254, which is 51 percent, break no rule at all: they are grammatical sentences that miss the job the question set. The remaining 240 are spread across a long tail of labels used only once or twice and too varied to group. That is an unfinished labelling job of ours rather than a third category.

An earlier version of this page reported those halves as 52 and 39 percent. The reason they moved is worth stating plainly: we wrote more judgment questions. The ACT did not change, and nothing was re-measured about it. The composition of this bank is a fact about our own authoring, which is also why it is the one thing on this page we can move on purpose.

One number that denominator excludes: a further 42 wrong answers in this bank still carry only a generic label rather than a named pattern, which is 2 percent of everything we labelled. They are not in the 2,453 and not in any percentage above. That figure was 281 when this was first published; the difference is a second labelling pass, not a change in the questions.

These are our own questions, written to match the current ACT, so the split describes our writers.

What the mechanics group contains

Punctuation is the biggest mechanical group at 205 of the 2,453. Subject and verb disagreement is next at 194. Then possessives, comma splices, fragments, tense shifts, misplaced modifiers.

Nothing on that list is surprising, which is the useful part. It is the material a grammar reference covers, and whether a given choice violates one of those rules has a determinate answer.

The second group is grammatical and still wrong

257 of the 2,453 fail a goal the question stated. What our reviewers wrote about those choices conveys it better than a definition: too broad to introduce the wall that stores heat; introduces a new topic instead of concluding the paragraph; specific, but about location and safety when the paragraph concerns changes in the bird's body.

Another 232 choose a transition naming a relationship the two sentences do not have, and 182 reach the right add-or-delete verdict for the wrong reason.

What these share is that no rule has been broken. Several choices can be correct English at once, so correctness is not what separates them.

Where the split is a judgment call

The two-group division is ours rather than a boundary inherent in the section. Redundancy is the clearest case: we filed it under judgment, since deciding "red in color" says the same thing twice is a writing decision rather than a rule violation, and filing it under mechanics would be equally defensible. Moving it shifts the split by several points, so treat the halves as approximate. Both groups are defined as explicit lists of labels, and a gate recomputes every number on this page from the question bank, so if the bank moves and this page does not, the build fails.

Reading the stated goal first

When a question names a goal, that sentence carries the instruction, and it is what the second group of choices is built against. Saying the goal in your own words before reading the options gives you something to judge them by other than whether they sound good, which on these items is not the distinguishing feature.

NO CHANGE is one of the answer choices, not an indication that a question carries no instruction. What varies is whether the question explicitly names a goal, and that can occur with or without NO CHANGE among the options.

For transitions, naming the relationship between the two sentences before reading the choices gives you the same kind of independent standard. ACT's English standards cover logical links between clauses as well as larger organisation, so the habit applies above the sentence too.

Preparing for one half only

That is the shape worth carrying away, and the exact figures will keep moving as we write more questions. If your preparation has only ever covered rules, it has only ever covered about half of what this section asks.