Hey team,

I checked out the pictures and really like your experimental design! Looks good! I'm looking forward to following along as your data starts to come in!

One small thing I just wanted to try to clarify because it is super important when designing your experiments. We are confusing our "variables" and our "data" a little bit.

In an experiment you have two kinds of variables - constant variables and experimental variables. Usually there are a lot of "constant variables" that you want to keep the exact same across all of your treatments, and then only one "experimental variable" that you are changing to look for an effect. In our case the experimental variable is the color of light that the radish plants are receiving. Our constant variables are things like how much and when you water the plants, the plant's photoperiod, the temperature of the room the plants are grown in, the type of soil you're using, the plastic cups that you planted the seed in, the type of plant that you're growing, etc. They're all things that you want to be the exact same for all of your plants. 

Then, once you have all of your constant variables and your experimental variable planned out, the next thing to decide is the data that you are going to collect during the experiment. Constant variables (such as the amount of water each day and the photoperiod) cannot also be part of your data. Those are variables that we are keeping the exact same during the experiment. We want to only collect data on the things that we think might be different in how the plants grow in the different light. 

So, the data we collect can also be broken up in to two categories -- "qualitative data" and "quantitative data". Qualitative data is data that you collect using words and descriptions to record changes in what you're seeing with the plants. So this would be things like how green the leaves look each week, what shape the leaves are, or what the plant smells like to you. Then, our quantitative data is data that you collect using numbers. So this would be things like how tall the plant is (in inches), the length and width of each leaf (in inches), the number of leaves produced by the plant, how much the plant weighs (in grams), etc. We should be collecting both types of data each week as the plants grow in the different light.

In your experimental design section, as a team I want you to list out these 4 groups: (1) As many "constant variables" as you can think of, (2) the one "experimental variable" for this experiment, (3) the "qualitative data" you're collecting, and finally (4) the "quantitative data" you're collecting. Remember, things that are constant variables can't be part of data that you're collecting. This is super important to do for every experiment you run. Even though I've done this hundreds of times as a graduate student, I still list out these four categories every time so that I am organized and know what I'm looking for!

Hope you all enjoy your weekend!

Bill

Good morning team!

Those are great ideas for things to document as the plants grow! I would consider all of those items (color change, how green they appear, "growth" of the leaves, and how full the plant looks to all fall in to a type of data category called "qualitative data", which is data that approximates and characterizes, and is non-numerical in nature. It is definitely worth tracking this type of data when running your experiments, but I also suggest trying to collect as much "quantitative data" as possible too. This is data this is numerical, such as your teams plan to measure how tall the plants are growing each week. There is lots of different "numerical" data items you could collect, and don't overwhelm yourselves but let's add a couple more! I'll throw out a few examples, but I want you as a team to think of a couple possibilities as well, and then decide which ~2-3 you want to add to track.

• The number of leaves that the radish plant has produced so far
• At the end, you could harvest the radish and measure the circumference and record the weight of the radish

Also, as a team let's decide how often you want to collect your data for each plant. I'm excited to see your results as you get started! Feel free to send me any questions!

- Bill

Questions and suggestions for you:

I think you have an interesting experiment planned and are in good shape to get some cool results! As I read through your experimental design, here are a few questions and ideas that I wanted to share:

• It would be worthwhile to list out all of the constant variables for your experiment -- the things that you want to remain the same across all treatments. It is important to try to think of as many of these as possible before starting the experiment so that you can be sure that only variable you are testing is the type of light. As an example, if it is possible, I would try to make sure that the day length for your potted radish plants under the grow tower is the same as whatever the day length is outside under natural light. Something like a cheap little lighting timer would do the trick.
  • I see that you listed the watering times and amount of water as items that will be constant for each treatment, which is an important constant! What are some other constants that you will have?
• Our lab at Cornell is actually doing research on how we can use UV light to control plant pathogens from growing on crops, including strawberries and grapes! We often use aluminum foil to either line the inside of boxes that we put plants in, or place aluminum foil on the table surface beneath the potted plants. It is great because it reflects all of the light back toward the plant, so the plants get maximum exposure. This might be a good idea for your boxes instead of painting them black!
• In addition to height, what are some other plant growth responses that you could measure over time? It is possible light may or may not affect plant height, but could affect plant growth in some other way. You want to be sure you catch that, so collect as many different types of data as possible!

Looks like you're off to a great start!

- Bill