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PSY100Y5 Introductory Psychology: Experiment Design

A short guide for helping with lab design and for locating empirical studies modeling experiments on human memory and recall.

Definitions: Hypothesis, Variables, Experimental Design

It is hard to design an experiment. Here is a quick guide from Science 101 at the University of California at Berkeley: "Design your own science experiment." Be sure to read the second page where all the good stuff is:

Here are some definitions adapted from the Science 101 page:

  • Research / Scientific Question is a question that may be answered by designing an experiment, gathering observations, and analyzing these observations.  It means that a research question should have a physical or natural answer. A question that cannot be answered with factual observations is not a good research question for the types of experiments you will be designing.
  • Hypothesis is a first try at an answer to your research question. Because the hypothesis is made before you do your experiment, it can be used as a prediction for what you expect your experiment to show. It may be helpful for you to write your hypothesis as an IF - THEN - BECAUSE sentence. 

For example, let's say your research question is "How should I spread ice-melting salt granules over an icy sidewalk to get the fastest ice melting action with minimal environmental side-effects?"

Your hypothesis may be: "Size of salt granules affects the ice melting action. IF I reduce the size of granules so as to spread them out more evenly, THEN I will get faster melting with same amount of salt used BECAUSE I will be able to improve area coverage per gram of salt."

  • Variables are things that can affect or change the progress of your experiment. In our ice salt example, variables include the size of salt granules, the amount of salt used, the brand of ice-melting salt you use, the kind of ice cover on your sidewalk, the sidewalk surface (concrete vs, interlock, etc.), the temperature, the amount of sunlight, and the sidewalk foot traffic. In psychology, variables will include participant age, prior experience, preparation, academic background, etc.
  • Independent Variable is what you change during the course of your experiment. In our ice salt example, the size of salt granules is what you change, so it is your independent variable.
  • Dependent Variable is that which responds to your change of the independent variable. In our ice salt example, the amount of melting of sidewalk ice is the dependent variable.
  • The control group in your experiment is that part of the experiment, or that part of the population under study, where you don't change the independent variable at all. In our ice salt example, the control would be a patch of the same sidewalk, equal in size, surface and temperature to the experimental patch, where you spread the same amount (by weight) of ice salt granules exactly as they come out of the bag, without changing their size.
  • Controlled Variables are things you want to keep the same during your experiment for both the control group and the experimental group. Controlled variables are not the same as your controls! In our ice salt example, the controlled variables should be: the amount of salt spread by weight (always the same!); sidewalk location, size and surface; temperature; amount of sunlight; amount or absence of foot traffic; etc.

So now you can get started!

Please refer to page 10 of the Publication Manual of the APA (2010) for more details on experiments in psychology. We have print copies of the Manual in the library at the reference desk (call number BF76.7 .P83 2010). No completely electronic copies of the 6th edition are available.

Here are the sections of a lab report, also described on page 10 of the APA Publication Manual:

  • Introduction, where you develop your research question by describing why you are studying it, including why it is an important question in psychology, and what work has been done on this problem before you got to it.
  • Method, where you describe what you did to get your data / observations.
  • Results, where you tell us what you found and how you calculated it: what were the actual observations? measurements and analyses?
  • Discussion, where you tell us what the results mean, for your experiment and for the discipline as a whole.

You may want to use this handy Assignment Calculator to help you with planning out and writing up the lab report. Be sure to select the Lab Report option:

 UTSC assignment calculator

To find empirical studies as models for your look for peer-reviewed journal articles reporting original research and refer to the tab in this guide called Find Articles


American Psychological Association. (2010). Publication manual of the American Psychological Association (6th ed.). Washington, DC: American

    Psychological Association.

University of California Museum of Paleontology. (2014). Design your own science experiment. In Understanding Science. Accessed on 3

    January 2014  at <>.

More about Memory

For a quick look into the basics of memory, including the role of recall, take a look at these two web-based resources:

  • Gale Encylcopedia of Psychology article on memory. Check out the diagram of memory processes.
  • Stages of Memory from Simply Psychology. This site helps with solidifying your grasp on what processes govern short-term memory (STM) and long-term memory (LTM).


Memory. (2001). In Strackland, B., Ed., The Gale Encyclopedia of

    Psychology. 2nd ed. Detroit: Gale, 2001. 415-8. Accessed on

    February 3, 2014, from the Gale Virtual Reference Library at

McLeod, S. (2007). Stages of memory: Encoding, sotrage and

    retrieval. In Simply Psychology. Accessed on February 3,

    2014, from

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