How do you spot and fix a comma splice or run-on between two independent clauses on the Digital SAT?
Avoiding comma splices and run-ons: recognising two independent clauses wrongly joined by a comma or by nothing, and choosing the correct fix (period, semicolon, comma plus conjunction, or subordination).
A focused answer to the Digital SAT skill of spotting and fixing comma splices and run-on sentences: recognising two independent clauses, applying the four valid fixes, and watching for conjunctive adverbs like 'however' that do not fix a splice on their own.
Reviewed by: AI editorial process; not yet individually human-reviewed
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What this skill is asking
A comma splice joins two independent clauses with only a comma; a run-on joins them with nothing at all. Both are errors, and the Digital SAT tests whether you can spot them and choose a valid fix. On the Digital SAT, the College Board (Standard English Conventions domain) builds boundaries questions where the wrong choices are splices or run-ons and the right choice applies one of the four valid joins. The skill is to confirm that both sides are independent clauses, then pick a correct fix.
Spot the splice or run-on
The first step is the same as every boundaries question: confirm that both sides of the punctuation are independent clauses. If they are, a comma alone or no punctuation is an error.
Apply the stand-alone test to each side. When both pass, you have two independent clauses, which means a comma by itself or no punctuation cannot be the answer.
The four valid fixes
Every comma splice or run-on is corrected by one of four moves. The choices usually contain one of these and three errors.
All four are grammatically correct; the SAT chooses among them based on which fits the sentence and the options offered. Recognising that these are the only valid fixes lets you eliminate any choice that uses a comma alone or no punctuation between two independent clauses.
The conjunctive-adverb trap
The most testable subtlety is the conjunctive adverb: "however," "therefore," "moreover," "consequently," "nevertheless." These feel like connectors, but they are not coordinating conjunctions, so a comma before one does not fix a splice.
This skill is the diagnostic complement to the rest of the boundaries module: where sentence boundaries and clauses teaches the joining patterns and semicolons, colons and dashes teaches the heavy marks, this page teaches you to recognise the error and reach for one of the four fixes, while sidestepping the conjunctive-adverb trap.
Exam-style practice questions
Practice questions written in the style of College Board exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Digital SAT R&W (style)1 marksWhich choice corrects the comma splice? 'The data were inconclusive, the researchers repeated the trial.' (A) inconclusive, the (B) inconclusive so the (C) inconclusive, so the (D) inconclusive theShow worked answer →
The correct answer is (C), "inconclusive, so the".
"The data were inconclusive" and "the researchers repeated the trial" are both independent clauses, so a comma alone (A) is a comma splice. A valid fix joins them with a comma plus a coordinating conjunction: "...inconclusive, so the researchers..." Choice (B) omits the comma before "so"; (D) removes the comma entirely, creating a run-on. The comma plus conjunction is correct.
Digital SAT R&W (style)1 marksWhich choice corrects the error? 'The bakery sold out by noon, however, it reopened the next morning.' (A) noon, however, it (B) noon; however, it (C) noon however it (D) noon, however itShow worked answer →
The correct answer is (B), "noon; however, it".
"However" is a conjunctive adverb, not a coordinating conjunction, so a comma before it (A) leaves a comma splice between two independent clauses. The fix is a semicolon before "however" (with a comma after it): "...by noon; however, it reopened..." Choice (C) is a run-on; (D) still splices with only a comma. A conjunctive adverb like "however" cannot join two independent clauses with just commas.
Related dot points
- Sentence boundaries and clauses: distinguishing independent clauses, dependent clauses and phrases, and choosing the punctuation that correctly joins or separates them on a Digital SAT boundaries question.
A focused answer to the Digital SAT boundaries skill of recognising independent clauses, dependent clauses and phrases, then applying the punctuation rules that join or separate them, the foundation for every boundaries question.
- Commas and coordination: using commas correctly with coordinating conjunctions, in lists, after introductory elements, and not between a subject and its verb, on Digital SAT boundaries questions.
A focused answer to the Digital SAT comma rules: the comma plus coordinating conjunction for two independent clauses, commas in a series, commas after introductory elements, and the rule against commas that wrongly split a subject from its verb.
- Semicolons, colons and dashes: using a semicolon between two independent clauses, a colon after a complete clause to introduce, and dashes to set off or emphasise, on Digital SAT boundaries questions.
A focused answer to the Digital SAT rules for semicolons (between two independent clauses), colons (after a complete clause to introduce a list or explanation), and dashes (to set off or emphasise), with the complete-clause test that decides each.
- Nonessential elements and supplements: setting off nonessential information with a matched pair of commas, dashes or parentheses, distinguishing essential from nonessential, and keeping the opening and closing marks consistent.
A focused answer to the Digital SAT supplements skill: setting off nonessential information with a matched pair of commas, dashes or parentheses, distinguishing essential (no commas) from nonessential (paired commas), and the rule that the two enclosing marks must match.
Sources & how we know this
- Reading and Writing: Content Domains and Skills — College Board (2024)
- Digital SAT Sample Questions — College Board (2024)