Marcus wants to test the effect of gravity on objects with different masses. He drops two footballs from a first-floor window, a second-floor window, and a third-floor window. In each case, he times how long it takes the footballs to reach the ground. What is wrong with his experimental design?
There are a few potential issues with Marcus's experimental design:
1. Lack of control: Marcus does not mention using the same type or size of football for each drop. This means that the mass of the football could vary between drops, which could introduce a confounding variable. To control for this, Marcus should use the same football for all drops.
2. No replication: Marcus only drops two footballs for each floor. This is a small sample size and may not provide enough data to draw accurate conclusions. To improve the experiment, Marcus should replicate the drops multiple times for each floor.
3. Only testing on one building: Marcus is only dropping the footballs from one first-floor window, one second-floor window, and one third-floor window. This restricts the generalizability of the results. To improve the experiment, Marcus should consider testing the effect of gravity on objects with different masses in various buildings or locations to ensure the results are not specific to one environment.
4. Ignoring air resistance: Marcus's experimental design assumes that air resistance has no impact on the footballs' descent. In reality, air resistance can influence the time it takes for an object to fall to the ground. To account for this, Marcus should consider using a vacuum or conducting the experiment in a controlled environment where air resistance can be minimized or accounted for in the analysis.
5. Lack of randomization: Marcus does not mention randomizing the order of the drops or the floors from which the footballs are dropped. Without randomization, there can be systematic biases in the results. To address this, Marcus should randomly assign the order of the drops and the floors from which the footballs are dropped to ensure balanced conditions.
Overall, Marcus's experimental design lacks control, replication, generalizability, consideration of air resistance, and randomization, which all limit the validity and reliability of the results.