Editing a lab report opening: three unclear sentences and one unsupported word
An undergraduate writes the following opening for a lab report on a temperature sensor:
'Having calibrated the sensor against a mercury thermometer, the readings were recorded at ten-minute intervals over six hours. The sensor output drifted by 0.8 °C, which proves that the amplifier was overheating, because the drift was monotonic and the lab was warm. Comparing the two sensors, the results were consistent to within ±0.2 °C for the first two hours but then diverged, and this is important. Data was collected using a calibrated datalogger, and the sensor was placed in a water bath that was stirred continuously and maintained the temperature.'
The supervisor marks three sentences as unclear and one word as unsupported, but says the underlying work is sound and all the measured claims are correct.
1. Identify the three clarity problems and name the grammatical fault in each.
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Dangling participle. 'Having calibrated the sensor …, the readings were recorded.' The implied subject of 'having calibrated' is the experimenter, but the subject of the main clause is 'the readings', which cannot calibrate anything. The agent disappears and the sentence becomes illogical. The same fault recurs in 'Comparing the two sensors, the results were consistent'. Fix: 'Having calibrated the sensor against a mercury thermometer, we recorded the readings …' or 'After the sensor was calibrated, readings were recorded …'.
Unclear relative pronoun / faulty reference. '… drifted by 0.8 °C, which proves that …' - 'which' can refer to the drift, to the magnitude 0.8 °C, or to the whole preceding clause, and these support different claims. Similarly 'and this is important' has no referent: the reader cannot tell whether 'this' is the agreement, the divergence, or the timing. Fix: name the antecedent - 'This divergence after two hours matters because …'.
Defective relative clause with a missing specification. '… a water bath that was stirred continuously and maintained the temperature' leaves 'maintained' without an object, so the reader cannot tell whether the bath was maintained or whether it maintained the temperature - and if the latter, at what value. Fix: 'a water bath stirred continuously and held at 25.0 °C'.
Minor, but worth flagging: 'Data was collected' is acceptable in British usage but inconsistent if the rest of the report uses 'were'.
2. The supervisor objects to the word 'proves'. Explain what the evidence actually licenses, and give a replacement.
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'Proves' claims deductive certainty, which an observational correlation cannot deliver. The evidence is: a monotonic drift of 0.8 °C over six hours, and a warm room. That is a temporal association plus a plausible mechanism, not a demonstration of cause. Several alternatives are not excluded by the design - sensor self-heating, a drifting reference thermometer, evaporation from the bath changing its temperature, or an ageing amplifier with any number of failure modes. No amplifier temperature was measured, and there was no control run at a stable ambient temperature.
What the data license is a statement of consistency: the drift is monotonic and the ambient was warm, so amplifier self-heating is a candidate explanation that should be tested next. Replacement wording: 'is consistent with the amplifier overheating' or 'suggests that the amplifier was overheating'. If the causal claim is to be kept, the report needs a measured amplifier temperature or a repeat run with the electronics cooled and everything else held constant - and that experiment should be proposed, not assumed.
3. Rewrite the paragraph in no more than 70 words, keeping every measured claim and dropping nothing that is factual.
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Model rewrite (66 words):
'After calibrating the sensor against a mercury thermometer, we recorded readings every ten minutes for six hours. The output drifted monotonically by 0.8 °C, a result consistent with amplifier self-heating, although the amplifier temperature was not measured. For the first two hours the two sensors agreed within ±0.2 °C and then diverged. The sensor was held in a continuously stirred water bath at a controlled temperature.'
What the rewrite does and does not do. It repairs all three faults: the calibrating agent is now 'we', the causal claim is downgraded to 'consistent with', and the bath clause has a subject and an object. It preserves every measured quantity: 0.8 °C, ±0.2 °C, ten-minute intervals, six hours, the two-hour threshold, and the monotonic character of the drift - the last of these is a factual observation and must not be silently dropped. It also adds the honest admission that amplifier temperature was not measured, which is what licenses the weaker verb. It does not add interpretation, because the opening of a report should report.