*This must be your own! Even though you are working with a partner all writing must be your own. You may brainstorm with your partner and create the same data table to collect the data in, but everything else must be uniquely yours!

Experimental Design Write-up example

  • What we’re testing:
  • The Effect of Nitrogen in Fertilizer on Sunflower Height
  • Variables:
  • Note: Independent variable is what you are changing to see if it causes a change. Dependent variable is what you are measuring to see if there is a change. Controlled variables are things that stay the same from trial to trail; you need at least 3 of them!
  • Independent: Added Nitrogen to Fertilizer (measured in grams)
  • Dependent: Sunflower Height (measured in feet)
  • Controlled: Amount of water, Amount of Sunlight, Amount of Fertilizer, Temperature, All seeds planted are of the same brand and package date, All sunflowers grown in the same greenhouse
  • Hypothesis:
  • Note: PLTW wants your hypothesis to be in “If, then” form.
  • If the amount of nitrogen in fertilizer increases, then the height of a sunflower will also increase.
  • Methods:
  • Note: It’s best to write steps in past tense now because that’s how it will be for the lab report, so this can be used in the lab report if you do a good job now!
  1. Five 25-Gallon Planting Pots were obtained and 20 gallons of Miloganite Brand Fertilizer was placed into each pot.
  2. The first pot served as the control and no additional nitrogen was added to the fertilizer.
  3. Additional nitrogen was added to the remaining four pots according to the table below:

Pot Number / Nitrogen Added (grams)
1 / 0
2 / 50
3 / 100
4 / 150
5 / 200
  1. The added nitrogen was mixed into the fertilizer to evenly distribute it throughout the fertilizer.
  2. One package of Burpee Brand Sunflower Seeds were evenly spread across the surface of the soil and gently pressed down into the soil about 2.5 inches beneath the surface and then covered loosely but fully by the fertilizer.
  3. All pots were placed on the same shelf in the greenhouse to ensure they all receive an equal amount of sunlight.
  4. The plants were left to grow for 8 weeks.
  5. Every day for 8 weeks each plant was given 1 liter of water. Other than that the plants remained untouched.
  6. After 8 weeks the heights of all plants in each pot were measured in feet (rounded to the nearest tenth) and then an average was taken to represent the pot.
  7. Data was organized into a table and a graph for visualization and analysis.
  • Data Collection:

Pot #1 / Pot #2 / Pot #3 / Pot #4 / Pot #5
Nitrogen (grams)
Number of Sunflowers
Heights of sunflowers
(feet)
Average Height of Sunflowers
(feet)