To increase the validity of his data, Mario could have:
### Added a 0 hours control:
Adding a control group with 0 hours of light would provide a baseline measurement of oxygen production without any light. This control group could help determine if there is any oxygen production in the absence of light, which would serve as a reference point for comparing the effects of different light exposures.
### Justification:
1. Baseline Measurement: A 0 hours control group would offer a baseline level of oxygen production. Any oxygen produced in this group would indicate photosynthesis-independent processes.
2. Comparison: By comparing the oxygen production in the 0 hours group with the other light exposure groups, Mario can better attribute the differences in oxygen production to the amount of light.
3. Scientific Rigour: Including a control group is a common practice in experiments to ensure the results are valid and can be attributed to the variable being tested—in this case, light exposure.
### Why the other options are less suitable:
- Reduce the number of plants: Reducing the number of plants would decrease the sample size, potentially leading to less reliable and less generalizable results. Larger sample sizes help mitigate individual variances and provide more robust data.
- Remove the 1 hour group: Removing data points, such as the 1 hour group, would reduce the range of the variable being tested. Having a broad range of light exposure durations is important for understanding the relationship between light and photosynthesis.
- Measure the oxygen in fiters: The term "fiters" is not clear, and assuming it meant "liters" or another unit of measurement, simply changing the measurement unit doesn't improve the validity of the experimental design or address the variability and comparison needs.
In conclusion, adding a 0 hours control group would most effectively enhance the validity of Mario's experiment by providing a necessary baseline and making his results more scientifically rigorous.
