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Paired-samples T-test

The Stroop task is when color words are printed in the wrong color; for example, the word red might be printed in the color blue. The conflict that arises when we try to read the words, but are distracted by the colors, increases our reaction time and decreases our accuracy. Several researchers have suggested that the Stroop effect can be decreased by hypnosis. Raz (2005) used brain-imaging techniques [i.e., functional magnetic resonance imaging (fMRI)] to demonstrate that posthypnotic suggestion led highly hypnotizable individuals to see Stroop words as nonsense words. Imagine that you are working with Raz and your assignment is to determine if reaction times decrease (remember, a decrease is a good thing; it indicates that participants are faster) when highly hypnotizable individuals receive a posthypnotic suggestion to view the words as nonsensical. You conduct the experiment on six individuals, once in each condition, and receive the following data; the first number is reaction time in seconds without the posthypnotic suggestion, and the second number is reaction time with the posthypnotic suggestion:
Participant 1: (12.6, 8.5)
Participant 2: (13.8, 9.6)
Participant 3: (11.6, 10.0)
Participant 4: (12.2, 9.2)
Participant 5: (12.1, 8.9)
Participant 6: (13.0, 10.8)

a. What is the independent variable and what are its levels? What is the dependent variable?
b. Conduct all six steps of a paired-samples t test. Be sure to label all six steps.
c. Report the statistics as you would in a journal article.

Solution Preview

a. Independent variable is the participant and its level is nominal scale. The dependent variable is the reaction time without posthypnotic suggestion and with the posthypnotic suggestion.

b. Six steps for a paired samples t test:

Step 1: stating the hypothesis
Ho: mu=0
Ha: mu is not equal to 0.
This alternative is two tailed and alpha=0.05.
Note: mu is the average difference between the two reaction times for the participants.

Step 2: check ...

Solution Summary

Paired-samples for t-tests are examined. The independent variables at all levels are determined.

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