To increase the validity of Mario's experiment in determining the effect of light on photosynthesis, he could consider several factors. The key to enhancing validity often lies in having a proper control, avoiding sample bias, and ensuring that measurements are accurate and appropriate. Here are the options given:
1. Reduce the number of plants: This is generally not a good practice for increasing validity. A larger sample size tends to give more reliable data by reducing the effects of outliers or random variations.
2. Remove the 1 hour group: Removing any group arbitrarily can reduce the comprehensiveness of the study. The 1-hour group provides valuable data on photosynthesis with minimal light, so removing it would actually decrease the validity of the results.
3. Add a 0 hours control: Adding a control group that receives 0 hours of light can significantly improve the validity of the data. This control serves as a baseline to compare the effects of different amounts of light on photosynthesis. It helps in confirming that the light is the factor causing the variations in oxygen production.
4. Measure the oxygen in liters: Changing the unit of measurement from milliliters to liters does not inherently increase the validity of the data. It simply scales the measurement but does not affect the accuracy or reliability of the data itself.
Therefore, out of the given options, the most appropriate action Mario could take to increase the validity of his experiment is to add a 0 hours control. This addition ensures that he has a baseline for comparison, thereby strengthening the conclusions drawn from the experiment.
