What would improve the validity of an experiment measuring the growth of bean plants using different fertilizers?

Improving the validity of an experiment is essential to ensure that the results accurately reflect the effect of the independent variable, in this case, the different types of fertilizers on bean plant growth. Including a control group without fertilizer is crucial for comparison. This control allows researchers to establish a baseline for plant growth under standard conditions. By measuring plant growth in both fertilized and non-fertilized conditions, one can determine the actual effect of the fertilizers.

This comparison helps to identify if any observed changes in growth are truly due to the fertilizers applied or if they could be attributed to other factors (such as natural growth patterns, soil nutrients, or environmental conditions) that would also affect plant growth. Without this control, it becomes challenging to interpret the results of the experiment accurately, thereby affecting the overall validity of the findings.

Maintaining other constants, such as water and sunlight, is also essential, but the presence of a control group is particularly pivotal to enhance the experiment's design.