Part 3: Fertilizer
Step 1 – Students’ prior knowledge assessed:
In the third part of the task, students were asked to consider how adding nutrients to the soil helped Plant A to grow. As with the sunlight investigations, students were asked to indicate their prior knowledge of how fertilizer affected plant growth. They were presented with the following information:
Fertilizer provides plants with materials they need to grow. These materials are called nutrients. How much fertilizer do plants need to grow well? Choose the statement below that you think is most likely to be true.
- Different kinds of plants need different amounts of fertilizer to grow well.
- Fertilizer does not help most plants grow well.
- The more fertilizer you give plants, the better they will grow.
- A little fertilizer will make most plants grow best.
Results showed that fourth-graders had a similar degree of prior knowledge about the effect of nutrients as they did about the effect of sunlight on plant growth. Over one-half (56 percent) of the students displayed “complex” prior knowledge; they already knew that different plants needed different amounts of nutrients. Eighteen percent displayed “simple” prior knowledge, and 26 percent of the fourth-graders provided responses that were rated “incorrect.”
Step 2 – Students perform fertilizer investigation:
Next, the experiment challenged students to answer the question, “How much fertilizer does Plant A need to grow best?” Students were presented with a screen image of six trays of Plant A which they were directed to drag onto the shelf of a greenhouse. For each tray of plants, students could opt to add up to nine scoops of fertilizer. The amount of fertilizer added to each tray was noted onscreen. Students were then told to click on the “Do Experiment” button on the screen; the plant images grew in height and sprouted leaves and flowers.
Results showed that 35 percent of students were able to strategically use the available trays to gather appropriate data on the effect of nutrients on plant growth. A correct experiment consisted of placing low, medium, and high numbers of scoops into the plant trays. In addition, correct experiments had to have at least one tray with 3 scoops of fertilizer and at least one tray with either 2 or 4 scoops of fertilizer.
About one third of each prior knowledge group (complex, simple, incorrect) from Step 1 did the experiment correctly. Only 21 percent of all fourth-graders who displayed “complex” prior knowledge were able to perform the experiment correctly. Approximately 6 percent of students who displayed “simple” prior knowledge were able to perform the experiment correctly. Nine percent of the fourth-graders whose prior knowledge was rated “incorrect” were able to perform the experiment correctly.
Try It Yourself: Users can perform the experiment using the animation presented onscreen.
Step 3 – Students draw conclusions:
After students moved their trays into place, conducted the experiment, and viewed their data table, they answered the following questions about
their conclusions for Plant A:
1. How many scoops of fertilizer does Plant A need to grow best? You may look at your data table again to help you with your answer.
- Options were the numbers 1 through 9
2.Remember that your classmate said: “Plants need nutrients to grow. So the more fertilizer Plant A gets, the better Plant A will grow.” Now that you have finished your experiments with Plant A and fertilizer, do you agree with your classmate?
3. Support your answer with specific observations and results from the data table. Type your answer in the box.
4. Based on your experiments in Parts 1, 2, and 3, which statement is most likely true?
- Most plants need some shade and some nutrients to grow well.
- Most plants need direct sunlight and some nutrients to grow well.
- Different kinds of plants need different amounts of sunlight and nutrients to grow well.
- The more sunlight and nutrients plants get, the better they grow.
Results showed that 56% of the students correctly indicated that Plant A needed 3 scoops of fertilizer to grow best. Forty-six percent were able to support their conclusion with information from the experiment.
Within each prior knowledge branch (complex, simple, incorrect), comparable proportions of fourth-graders were able to give complete explanations of their performance on the experiment. Twelve percent of all fourth-graders who displayed “complex” prior knowledge and did the experiment correctly were able to give complete explanations. Three percent of fourth-graders who displayed “simple” prior knowledge and did the experiment correctly were able to give complete explanations. Five percent of fourth-graders whose prior knowledge was rated “incorrect” and did the experiment correctly were able to give complete explanations.
Try It Yourself: Users can perform the experiment, view the data table, and then draw conclusions using the animation presented onscreen.
SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2009 Science Assessment.