Experimenters will need a supply of Coke, Pepsi, plastic or paper cups, and a larger cup of water for each subject.

Cola Taste Test

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Concepts illustrated: reverse counterbalancing; single-blind procedure; two-level repeated measures design

Competing producers of cola products always to claim that their drink is the best and will be preferred by others in “taste tests.” Such tests are often biased in ways favoring the cola company sponsoring the taste test, however. This lab will use a single-blind procedure and the proper use of counterbalancing to yield a semi-unbiased assessment of the relative merits of two cola products (i.e., “semi” because a double blind would be a better procedure, but a single blind is more manageable with lab partners. Coke and Pepsi will be the products for comparison.

You will need to have 1 lab partner for this experiment (friend or family member). The experimenter setting up the procedure will pour equal amounts of the drinks into small plastic cups and place the cups on a table at which a participant will sit. Each participant will test four drinks and the drinks will be presented in a sequence determined by a reverse counterbalancing procedure. The simplest way to assign subjects to an order is for the instructor to prepare file cards with the sequences on them, and then hand them out to the lab partners at the start of the exercise.

Half of the participants in the lab will receive this sequence:

Coke – Pepsi – Pepsi – Coke [ CPPC ]

The remaining participants in the lab will receive this sequence:

Pepsi – Coke – Coke – Pepsi [ PCCP ]

Procedure:

  • Experimenters will need a supply of Coke, Pepsi, plastic or paper cups, and a larger cup of water for each subject.
  • A coin toss determines who goes first as Experimenter. After the experiment has been completed, the two lab partners reverse roles.
  • The Experimenter prepares the drinks in equal amounts in unmarked cups, and lines them up in the proper sequence in front of the participant. The subject should drink all of the liquid from the first cup, then give a response for each of the three rating scales (below). After completing the first drink, the participant drinks some water to remove the aftertaste of the first drink, and then samples the second drink. This sequence of drink the liquid—rate the drink—drink the water continues until all four of the drinks have been sampled.
  • After tasting each drink, participants will give verbal ratings for sweetness, aftertaste, and overall liking. That is, after drink has been consumed, the Experimenter will ask (and record the verbal responses):
  • After all four drinks have been sampled, have experimenters ask subjects to guess which sequence of drinks they experienced. This will enable an analysis of subject’s ability to distinguish Coke from Pepsi. You may refer to this lab activity in Chapter 7 when describing two-level repeated measures designs and the dependent samples t-test.

1. On a scale from 1-10, with 1 meaning not at all sweet and 10 meaning extremely sweet, how would you rate the sweetness of the cola you just drank?

2. On a scale from 1-10, with 1 meaning no aftertaste and 10 meaning a very strong aftertaste, how would you rate the aftertaste strength of the cola you just drank?

3. On a scale from 1-10, with 1 meaning strong dislike and 10 meaning a strong liking, how would you rate the overall quality of the cola you just drank?


Data Summary:

For each participant, combine the ratings for each of the two drinks that were the same brand. That will yield, for each participant, a 20-point scale for sweetness, aftertaste, and quality for both drinks.

Record the data for your participant below:

trial 1 trial 2 total

Coke sweetness ________ + ________ = ________

Coke aftertaste ________ + ________ = ________

Coke liking ________ + ________ = ________

trial 1 trial 2 total

Pepsi sweetness ________ + ________ = ________

Pepsi aftertaste ________ + ________ = ________

Pepsi liking ________ + ________ = ________

Experimenter ________________________________________________

Participant ________________________________________________


Retrieved from: Research in Psychology, IM.7e, La