ACT (Enhanced)ScienceHard
A student is designing an experiment to determine if the color of light affects the growth rate of radishes. They plan to grow 30 radish plants in each of four conditions: natural sunlight, red light, blue light, and green light. All plants will receive the same amount of water, soil, and temperature. After 3 weeks, the height of each plant will be measured. To ensure the reliability of their results, which of the following actions is most crucial?
- AMeasuring the plant height only once at the end of the experiment.
- BUsing only one radish plant per light condition.
- CRepeating the entire experiment multiple times and averaging the results.
- DUsing different types of radish seeds for each light condition.
Show answer & explanationAnswer & explanation
Correct answer: C. Repeating the entire experiment multiple times and averaging the results.
Repeating the entire experiment (replication) helps confirm that the observed results are consistent and not due to random chance or unaccounted-for variables in a single trial. Averaging results from multiple repetitions increases the statistical reliability and validity of the conclusions.
Why the other options are wrong
- A. Measuring only once is acceptable for the final height, but replication of the entire experiment is key for reliability, not just measurement timing.
- B. Using only one plant would severely limit statistical power and make results unreliable due to individual variation.
- D. Using different types of seeds would introduce another uncontrolled variable, making it impossible to isolate the effect of light color.
Experimental Reliability
The consistency and repeatability of experimental results; reliable experiments produce similar outcomes when repeated under the same conditions.
- Achieved through replication and consistent methodology.
- Distinguished from validity (measures what it's supposed to).
- Essential for drawing trustworthy scientific conclusions.
Memory trick: Reliability: Can I 'rely' on these results if I do it again?