Science Buddies: "Ask an Expert"

I am almost done with my science project and would live to interview someone about how I did and if the data I collected makes sense. My scientific question is: What is the effect of different colored lights on a radishes growth. I predicted that the red light would have the tallest radish. Here is my data:
http://nces.ed.gov/nceskids/createagrap ... e39ca96d1a (Go to preview)
To conduct my experiment I planted 4 radishes under different colored light. Then every 3 days I measured he tallest plant. And water each plant 1/2 cup.

Do you think my data works?
Is there anything I could have done better or differently in conducting my experiment?
What could I have done better in conducting my experiment?
Is there anything I could have done to mess up my data?
Thanks

Hi,

First of all, congratulations on getting so far with your science project. I have one main question about your experiment: Did you only use one radish plant for each color light (i.e. four radishes total) or did you plant multiple plants for each color of light. The way you've described your data so far, and from your graph, it looks to me like you only used one plant for each light color. The problem with that is that your radish plants aren't exactly identical to each other, so one might naturally grow taller than another even if they were all grown under the same light (just like the plants in a garden aren't all exactly the same height, even though they all are getting the same sunlight). To help account for that, scientists like to use something called replicates. Ideally, you would have a minimum of three plants for each type of light, and then you could average the heights for your three plants. This would help you control for any natural differences in the plants.

That said, you did a great job formulating a hypothesis, and it's great that you mentioned that you watered each plant precisely 1/2 cup. It's very important to control variables like that, so good job!

In the end, while your experiment would be much more conclusive with more plants, I don't think you "messed up" your data. Your hypothesis didn't necessarily turn out to be true, but that is a natural part of science. I think you can say that the plant under the pink light grew the tallest, but that in order to be sure that this is due to the different wavelengths of light, you would need to repeat the experiment and get similar results.

I hope this helps!
JMP

I agree with JMP, and I want to emphasize that results that do not confirm the hypothesis are normal, and perhaps more common than those that fit the original hypothesis. The challenge now is to try to understand why the results differed from the hypothesis, and as JMP suggested, perhaps to repeat the experiment.

Remember the steps of the scientific method: https://www.sciencebuddies.org/science- ... ificmethod

Analyze Your Data and Draw a Conclusion: Once your experiment is complete, you collect your measurements and analyze them to see if they support your hypothesis or not.
Scientists often find that their hypothesis was not supported, and in such cases they will construct a new hypothesis based on the information they learned during their experiment. This starts the entire process of the scientific method over again. Even if they find that their hypothesis was supported, they may want to test it again in a new way.

Cheers,
Colin

Hi there,

I agree with both of the previous experts. I'd also like to emphasize that what JMP mentioned about having replicates is very important since there is natural variability between radish plants; however, I think you've done a great job formulating a hypothesis and carrying out your experiments! When you first started off with your experiments, did you plant 4 different seeds in soil and then put each of them under a different colored light, or did you start out with radish plants that have already sprouted? If you started out with seeds, did you weigh those seeds to see if they are around the same weight? Because if you start with seeds with drastically different weights, that could be one factor that may cause the plants to grow differently in addition to the light you've provided. If you started out with radish plants that have already sprouted, if there are differences in height to begin with, that could also be a factor influencing differences in growth. These are things to keep in mind as you are writing up your results. Also, out of curiosity, why did you think that red light will cause the radish to grow more out of all the different colors? Is there a reason behind why you think this? Because if there is, it may be useful to mention this in the introduction or in your hypothesis when you are writing up your report or presenting your results.

Let us know if you have anymore questions.

Connie