Unclear Reference in a Lab Report
In a lab report on water filtration, a student writes: 'After the samples were heated, they were placed in the centrifuge.' Later: 'The flow rate increased when the catalyst was added, which was unexpected.' And: 'The solution was filtered through the membrane, and it was then analyzed.' The teaching assistant marks the report down for 'unclear reference' but does not say which words are unclear. The student believes the sentences are fine because each one is grammatical and the reader can 'figure out' the meaning from context. The TA's rubric awards 10 points for clarity and 5 for grammar. The report is due in two days, and the student wants to revise only the sentences the TA actually flagged.
1. Identify the unclear reference in each of the three sentences and explain what makes it unclear.
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Sentence 1: 'they' could refer to 'samples' or to an unstated agent (the researchers). Grammatically 'they' most naturally attaches to 'samples,' but samples are not usually the thing placed in a centrifuge by themselves. Sentence 2: 'which' can attach to the whole event (the increase was unexpected) or to the nearest noun (the catalyst was unexpected). The reader cannot tell whether the surprise was the rate increase or the catalyst. Sentence 3: 'it' could be the solution or the membrane, though context favors the solution. In each case the ambiguity is structural, not lexical: the pronoun or relative clause has more than one grammatically available antecedent. That is why the sentences can be grammatical and still unclear.
2. Revise all three sentences. Explain why your revisions are clearer rather than just longer.
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Revisions: (1) 'After heating the samples, the technician placed them in the centrifuge.' (2) 'The flow rate increased when the catalyst was added; this increase was unexpected.' (3) 'The solution was filtered through the membrane and then analyzed.' Changes: (1) names the agent, so 'them' has one referent; (2) replaces 'which' with a noun phrase ('this increase'), which pins the referent; (3) removes the second clause's pronoun and uses a parallel verb. None of these additions is padding. Each removes a possible misreading. Clarity here is not about sentence length; it is about giving each referring word exactly one available antecedent. The revisions are therefore justified by function, not by a preference for longer prose.
3. The student says context lets readers 'figure out' the meaning. When is that defense acceptable?
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Context can rescue a reference when only one interpretation is plausible and the cost of error is low. It is not acceptable when the ambiguity concerns the method or the result, because a reader cannot verify what was done. In a lab report, 'which was unexpected' matters: if the catalyst itself was unexpected, that is a different finding from an unexpected rate increase. The test is whether a careful reader could reasonably choose the wrong antecedent and draw a different conclusion. If yes, revise. If no, and the sentence is otherwise clear, context is enough. The student's defense is therefore sometimes valid but does not cover sentence 2, where the two readings produce different scientific claims.