📝 Repetition and replication in experiments (12 MCQs)
📖 From Campbell Biology • 1. Evolution and the theme of Biology and Scientific Inquiry • 12 questions available
What is Repetition and replication in experiments?
Definition:
Repetition and replication in experiments are fundamental principles of scientific rigor, where repetition involves performing the same experiment multiple times within the same study to verify internal consistency, while replication involves independent researchers repeating the experiment to confirm the findings, and both are essential for establishing the reliability and generalizability of scientific results, ensuring that they are not due to chance or artifacts.
Working:
Repetition works by having multiple replicates (e.g., 10 test tubes, 20 mice) within a single experiment to account for biological variability and minimize error; replication works by other labs using the same or similar methods to test the findings, and if the results are reproducible, the evidence is strengthened; statistical analysis, such as calculating the mean and standard deviation, helps quantify variability, and the -value indicates the likelihood that results are due to chance, with replication being the gold standard for validating scientific discoveries.
Example:
A simple example is a study measuring the growth of bacteria in response to an antibiotic: repetition would involve growing multiple cultures under the same conditions and averaging the results; replication would involve another lab independently conducting the same experiment; if both yield similar results, the conclusion that the antibiotic inhibits growth is robust, illustrating the importance of repetition and replication.
Reason:
Repetition and replication are vital to avoid false positives, build confidence in findings, and allow the scientific community to build upon reliable data, and they are essential for translating research into practical applications, making them a hallmark of scientific practice.
📝 All Repetition and replication in experiments MCQs
Q1. A researcher observes a population characteristic once and obtains an unusual result. Which next step most directly increases confidence that the finding reflects a consistent biological pattern rather than random variation?
📖 Explanation: Repeating observations with comparable conditions and independent samples helps determine whether a result is reproducible. A single unusual observation may arise from sampling variation, measurement error, or an uncontrolled factor, so repetition provides stronger evidence.
Q2. Why does repeating an experiment strengthen a scientific conclusion even when every repeated trial does not produce exactly the same numerical result?
📖 Explanation: Biological systems and measurements naturally vary, so repeated trials rarely produce perfectly identical values. Consistency in the overall pattern, despite reasonable variation, provides stronger evidence than a single measurement.
Q3. Two laboratories independently test the same hypothesis. Laboratory A obtains a strong effect in five trials, while Laboratory B obtains a smaller effect in five trials but the same direction of change. What is the best interpretation?
📖 Explanation: Independent repetition can support the reliability of a pattern even when effect size differs. Differences may result from environmental conditions, populations, measurement methods, or other variables that should be investigated rather than ignored.
Q4. A student tests whether light intensity affects plant growth. The first trial uses 3 plants under each light condition and shows a difference. The student concludes that light intensity definitely causes the difference. Which reasoning is strongest?
📖 Explanation: A small initial trial can provide useful evidence but does not justify certainty. Repeated trials, adequate sample sizes, and appropriate controls help determine whether the observed difference is reproducible rather than chance-driven.
Q5. A team repeats an experiment three times. In Trial 1, treatment increases the measured response; in Trial 2, it has little effect; in Trial 3, it again increases the response. Which conclusion is most scientifically defensible?
📖 Explanation: Two trials showing the same pattern provide evidence for a reproducible effect, but the inconsistent second trial should not simply be ignored. Researchers should investigate possible uncontrolled variables, measurement problems, or natural variation.
Q6. A researcher obtains the same result every time but uses a measuring instrument that is consistently miscalibrated in the same direction. What does this example demonstrate about repetition?
📖 Explanation: Repeated measurements can reveal high consistency while still being wrong if the same systematic error affects every trial. Repetition primarily helps assess reproducibility; calibration and independent validation are also needed for accuracy.
Q7. A biologist repeats an experiment but changes temperature, sample size, and measurement technique simultaneously. The repeated experiment gives a different result. What is the main problem with using this repetition to evaluate the original finding?
📖 Explanation: A useful repetition should preserve the relevant experimental structure closely enough to permit meaningful comparison. When several variables change simultaneously, the source of a changed outcome becomes ambiguous, weakening the ability to assess reproducibility.
Q8. A researcher reports that a treatment increased enzyme activity by 20% in one trial. A colleague repeats the procedure four times and obtains increases of 18%, 21%, 19%, and 22%. Which interpretation is best?
📖 Explanation: The repeated values are close to the original observation and consistently show an increase. Small numerical differences are expected in biological measurements, so the repeated pattern provides stronger evidence of reproducibility.
Q9. The table shows the number of successful repetitions supporting a predicted effect: Trial group A: 2 of 5; B: 4 of 5; C: 5 of 5; D: 3 of 5. Which group provides the strongest evidence that the observed effect is reproducible?
📖 Explanation: Group C has the highest proportion of successful repetitions, with all five trials supporting the predicted effect. Assuming comparable conditions and independent trials, this consistency provides the strongest evidence for reproducibility among the groups.
Q10. A researcher compares two methods for testing the same biological response. Method X produces nearly identical results across repeated trials, while Method Y produces more variable results but has an independent calibration showing greater accuracy. Which conclusion is most appropriate?
📖 Explanation: A method can be highly precise yet systematically inaccurate, while another can be more accurate but variable. Repetition assesses consistency, but method selection should also consider calibration, validity, sources of variation, and experimental purpose.
Q11. A scientist observes that increasing nutrient concentration appears to increase growth. Repeated trials reproduce the pattern only when temperature remains within a narrow range. Outside that range, the relationship disappears. What is the best interpretation?
📖 Explanation: Repetition under different conditions can reveal limits to a pattern rather than simply confirming or rejecting it. The results suggest that nutrient effects may depend on temperature, an important mixed-variable consideration.
Q12. A researcher claims, 'Because my experiment produced the same result in every repetition, alternative explanations are impossible.' Which criticism is strongest?
📖 Explanation: Perfect reproducibility does not automatically establish causation or eliminate systematic error. A biased procedure, confounding variable, or flawed measurement can repeatedly produce the same pattern, so repeated results must be evaluated alongside controls and alternative explanations.