A zoologist observed that a small beetle larva, Psephenus herricki, was found on rocks covered with
unicellular algae in stream with rapid currents. The zoologist asked the following question: “Does the
presence or absence of algae influence whether or not these beetle larvae found on rocks?”
a) Describe a testable hypothesis for investigating this question.
b) Design an experiment to test your hypothesis.
c) Identify the in dependent variable in your experiment.
d) Identify the dependent variable(s) in your experiment.
e) Identify the controlled variables in your experiment.
Answers
Answer:
a.)For a hypothesis to be testable means that it is possible to make observations that agree or disagree with it. If a hypothesis cannot be tested by making observations, it is not scientific
b.)Experimental design means creating a set of procedures to test a hypothesis.
A good experimental design requires a strong understanding of the system you are studying. By first considering the variables and how they are related (Step 1), you can make predictions that are specific and testable (Step 2). How widely and finely you vary your independent variable (Step 3) will determine the level of detail and the external validity of your results. Your decisions about randomization, experimental controls, and independent vs repeated-measures designs (Step 4) will determine the internal validity of your experiment.
Step 1: Define your research question and variables
Step 2: Write your hypothesis
Step 3: Design your experimental treatments
Step 4: Assign your subjects to treatment groups
c-d.)The dependent variable is the variable being tested and measured in an experiment, and is 'dependent' on the independent variable. An example of a dependent variable is depression symptoms, which depends on the independent variables.The independent variable is the variable the experimenter manipulates or changes, and is assumed to have a direct effect on the dependent variable. For example, allocating participants to either drug or placebo conditions (independent variable) in order to measure any changes in the intensity of their anxiety (dependent variable).
e.)A control variable (or scientific constant) in scientific experimentation is an experimental element which is constant and unchanged throughout the course of the investigation. Control variables could strongly influence experimental results, were they not held constant during the experiment in order to test the relative relationship of the dependent and independent variables. The control variables themselves are not of primary interest to the experimenter.