Biology Regents Practice Exam

In an experiment on the effect of water temperature on aquatic snails, how could the student improve the experiment's validity?

1. Alter the pH of the water.

2. Change the size of the tank.

3. Carry out the experiment for a shorter period of time.

4. Use a larger number of snails.

The correct answer is: Use a larger number of snails.

Using a larger number of snails in the experiment increases the validity of the results by enhancing the reliability and robustness of the data collected. A larger sample size reduces the influence of random variations or outliers, allowing for more accurate estimations of the average effect of water temperature on snail behavior or physiology. In biological experiments, having more subjects can lead to results that are more representative of the population being studied. This is important because it helps ensure that conclusions drawn are more likely to reflect true patterns rather than being artifacts of a small sample size. In contrast, altering environmental conditions like the pH of the water or changing the size of the tank could introduce additional variables that may confound the results. Carrying out the experiment for a shorter period could limit the observations and findings, potentially missing crucial data relevant to understanding the long-term effects of temperature on the snails. Therefore, increasing the number of snails directly enhances the experimental design and confidence in the conclusions drawn from the data.