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Wednesday, October 12, 2011

Science Skills: Let the Student Design the Experiment!



Student Designed Experiment: Applying the Scientific Method


In my many years of teaching, I have discovered that my students do not truly understand how to apply the scientific method.  When they reach my high school biology class, they can recite the steps to the scientific method, but few can actually design a controlled experiment.   Most science teachers (me included!) have our students complete “cookbook” labs in which the student follows a list of steps and hopefully reaches the desired outcome or conclusion.    I am trying to move away from this approach and make my labs more inquiry driven.  This is no easy task!!  Due to overloaded classes, time constraints  and nonexistent budgets, few science teachers can take a class to the lab and turn them lose to be “little scientists”.

With all of that in mind, I have written this “Student Designed Experiment” that has worked very well for me.  Here are the main points:

  • In this activity, all students will be designing a lab on the same topic and using the same simple materials. 
  • Students are asked to design an experiment to determine how various quantities of water will affect the germination of seeds.
  • There are very few variations as to how to design this experiment.   This keeps all of your students moving in about the same direction.  This makes your role as facilitator easy, especially if class size is large.  If this is the first time your students have tried to design their own experiment, the limited possibilities in experimental design will help your students learn the process with less frustration.
  • This requires very simple materials:  Petri dishes or other similar container, radish seeds, graduated cylinder, and water.
  • In this activity, students are asked to identify the independent and the dependent variables.  They must also describe their experimental group and their control group.
  • Students must design a data table and construct a graph of the data they collect.
  • The handouts that I have developed for this activity can be used over and over.  If you have another idea for a ”student designed experiment”, you can have your students use these same handouts.
  • If time allows, you might want to have your students design a second experiment that tests a different variable, such as the effect of temperature on seed germination or the effect of pH on seed germination. 

This is somewhat time consuming, but in my opinion, is well worth the time.  This lesson cannot be completed in one class period.  I require that students first submit their experimental design to me for approval.  I make suggestions, and have the students refine their experiment.  Next, students are in the lab to actually carry out their experiment.  Students must return to the lab at different time intervals to count their germinated seeds.  Students must analyze their data, graph the results, reach a conclusion, and turn in their final packet of work. 


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