Activity: Design an Experiment

Experimental Design Activity for Chapter 2 


n      You will design a taste-testing experiment in which subjects will be asked which of two similar items tastes better to them.  However, the issue is not which item the subjects prefer, but rather whether or not preferences are different when you know what is being tasted.  Blinding subjects is an important precaution in testing a new medical treatment because subjects might be influenced by the idea of being treated.  We want to design a study to see if blinding is also an important issue for taste-testing experiments.  For example, perhaps people will tend to state a preference for a more expensive item because they think they are supposed to like it better.


n      Your group will develop the protocol for a designed study of blinding in a taste-testing experiment.  You should be prepared to present your protocol to your lab and to defend the choices you make.


n      Here are some examples:

    n      A non-fat yogurt versus a regular yogurt of the same brand

   n      Kellogg’s corn flakes versus a store brand of corn flakes


n      Orange juice from a carton versus freshly squeezed orange juice


n      French fries cooked in a microwave versus the same brand cooked in a conventional oven

n      It is important to remember that the purpose of the experiment is to find out if knowing what is being tasted makes a difference to people’s preferences.  Thus, in your protocol some of the subjects should be told in advance which item they are tasting, while the other subjects will not be told.

n      A protocol is a complete experimental plan.  Write a couple of paragraphs in which you describe your protocol.  Your protocol should describe the following: 

     n      What are your independent and dependent variables?

     n      Precisely what are the two items being tested

     n      How the items will be served (For example, will the corn flakes be served with non-fat, low-fat, or regular milk?)

     n      How you will decide which item to present first and which to present second

     n      How you will determine which subjects are to be blinded and which will be told what they are tasting

     n      What other special precautions you will take to eliminate possible confounding variables.