Experimental Design

This worksheet is designed to help you organize your thoughts about this experiment and devise a hypothesis.
Before doing this, you will have to work through all of these questions with your group and ask me about your
experiment. Download this worksheet and type your answers in (10 points).

  1. Experimental question (2 pts): What question do you want to test using the nematodes? In your question, be
    sure to include your independent and dependent variables. The independent variable is the factor being
    manipulated or changed by the researcher. The dependent variable is the product of changing the independent
    variable; these are your results.
  2. Hypotheses (2 pts): In order to set up your experiment, you will need to formulate a hypothesis. You will
    have both a null and alternative hypothesis. The null hypothesis is the one we test, the alternative hypothesis
    contradicts the null hypothesis; it is probably the one we favor. We accept or reject the null hypothesis based
    on the outcomes of the experiment. In actual practice, it is difficult to prove the null hypothesis is true, so if we
    reject it, then our alternative hypothesis gains credibility.
    A null hypothesis says that the independent variable has NO effect on the dependent variable. An alternative
    hypothesis says that the independent variable does have an effect on the dependent variable. THE
    Let’s try an example: You are testing the effect of a fertilizer on plant growth. Your control group will not receive
    the fertilizer and your experimental group will receive it. Otherwise, all of the conditions for growth will remain
    the same. At the end of the experiment, you will measure plant growth by harvesting, drying and weighing the
    Your null hypothesis is, “The fertilizer will not affect plant growth.”
    Your alternative hypothesis will be, “The fertilizer will affect plant growth.” Note that you do not need to say
    whether the fertilizer will help or harm plant growth.
    Write your null and alternative hypotheses for the nematode experiment.
    Null Hypothesis:
    Alternative Hypothesis:
  3. Experimental Design (4 pts): Describe how you will set up your experiment in order to answer your question.
    • How will you differentiate between your control and experimental group(s)?
    • Describe what will happen in each group.
    • How many replicates in each treatment should there be (remember you will need to calculate a mean for
    each group)?
    • Draw a picture of the experimental design.
  4. List of materials (1 pt): Please list and give a count for all of the things you will need. I will use this as a
    shopping list.
  5. Predictions (1 pt): Make predictions about what you think will happen. Say why you think this.

Sample Solution