Revising a Run-On Sentence in a Lab Report
A student writes this sentence in a lab report: "The samples were stored at four degrees for six hours the enzyme activity was measured every thirty minutes the results showed a steady decline however the control group remained stable." The teacher marks it "run-on" and asks for revision without changing the meaning. The student's first attempt reads: "The samples were stored at four degrees for six hours, the enzyme activity was measured every thirty minutes, the results showed a steady decline, however, the control group remained stable." The teacher marks this attempt "comma splice" and returns it again. The student has a word limit of 40 words for the sentence and must keep all four ideas.
1. Diagnose what is wrong with the original sentence and with the first revision, naming the specific errors and explaining why adding commas did not fix the problem.
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The original is a fused sentence, also called a run-on: it strings together four independent clauses with no punctuation or conjunction. Each clause has its own subject and verb: the samples were stored, the activity was measured, the results showed, the control group remained. Written end to end, the reader cannot tell where one idea stops and the next begins.
The first revision adds commas but keeps the same four independent clauses joined only by commas. That is a comma splice, which is the same error in a different costume. A comma is not strong enough to join two independent clauses by itself. The word "however" does not rescue it, because "however" is a conjunctive adverb, not a coordinating conjunction; when it joins two independent clauses it needs a semicolon before it and a comma after it, as in "decline; however, the control group remained stable."
The deeper problem is structural, not punctuation. The student is trying to fix four clauses with marks when the sentence needs either stronger connectors or a change in clause structure, such as subordinating one idea to another.
2. Write a revised sentence of no more than 40 words that keeps all four ideas and is grammatically correct. Then explain the choices you made and why they satisfy the word limit.
Read the worked answer
Revision: "Samples were stored at four degrees for six hours, and enzyme activity was measured every thirty minutes; results showed a steady decline, but the control group remained stable." That is 30 words, within the limit.
The revision uses three techniques. First, a comma plus "and" joins the storage and measurement clauses, which are closely related steps. Second, a semicolon joins the measurement clause to the results clause, signaling that the results follow from the procedure while keeping the two independent clauses distinct. Third, a comma plus "but" joins the decline to the stable control, and "but" correctly marks the contrast that "however" was trying to carry.
I also cut "The" from the opening and changed "the enzyme activity" to "enzyme activity" and "the results" to "results," which is standard in lab reporting and saves words. No idea was dropped: storage conditions, measurement interval, declining activity, and a stable control all remain. The sentence is now four clauses joined by connectors strong enough for independent clauses, so it is neither a run-on nor a comma splice.