Question

To examine whether planting trees reduces air pollution, we find a sample of city blocks with similar levels of air pollution and we then plant trees in half of the blocks in the sample. After waiting an appropriate amount of time, we measure air pollution levels.

Short answer

The best way to draw a conclusion from this experiment is to examine the relative change in pollution levels in the city blocks where trees were planted compared to those where no trees were planted. This can provide us with quantitative data on the effectiveness of tree planting in reducing air pollution.

Step-by-step solution

Understanding the Experiment Setting

The first step is to understand the setting and the nature of the experiment. The experiment involves taking a sample of city blocks that have similar levels of air pollution. Trees are then planted in half of these blocks.

Conducting the Experiment

Upon planting trees in half of the selected city blocks, an appropriate amount of time needs to be given to see the effect of the trees on the levels of air pollution. This could be a few months to a few years, depending on various factors like the type of tree, growth rate, local climate, among other things.

Collect Data

After waiting for an appropriate amount of time, the air pollution levels on the city blocks are measured again. This data will be compared to the data that were initially collected before the experiment.

Analyze Results

Once the new air pollution levels are measured, analyze the results by comparing the air pollution levels. If the air pollution levels in the blocks with trees are significantly lower than the blocks without trees, then it can be inferred that planting trees does help reduce air pollution levels. If there is no significant difference, then we might need to reconsider our hypothesis.