Configure mkcontrast-sess: Difference between revisions
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Contrasts are embodiments of hypotheses that you want to test. They are linear combinations of conditions. In order to construct a contrast, you need to know the numeric ID associated with each condition; this is specified in your [[Par-Files|paradigm file]]. | Contrasts are embodiments of hypotheses that you want to test. They are linear combinations of conditions. In order to construct a contrast, you need to know the numeric ID associated with each condition; this is specified in your [[Par-Files|paradigm file]]. | ||
Suppose, for example, your par-files for an experiment were encoded with the following conditions: | |||
1 nonword | |||
2 low-frequency word | |||
3 high-frequency word | |||
Contrasts between conditions are vector weightings of each condition. | |||
The key thing is that the <u>'''a'''</u>ctivated and <u>'''c'''</u>ontrast weightings must sum to zero. Continuing with this example, to configure the words > nonwords contrast for the analysis specified by the previous call to <code>mkanalysis-sess</code>, you would run the following command within your $SUBJECTS_DIR: | |||
mkcontrast-sess -analysis booth500.sm6.lh -contrast words-v-nonwords -a 2 -a 3 -c 1 | |||
Revision as of 16:39, 14 April 2016
Contrasts are embodiments of hypotheses that you want to test. They are linear combinations of conditions. In order to construct a contrast, you need to know the numeric ID associated with each condition; this is specified in your paradigm file.
Suppose, for example, your par-files for an experiment were encoded with the following conditions:
1 nonword 2 low-frequency word 3 high-frequency word
Contrasts between conditions are vector weightings of each condition.
The key thing is that the activated and contrast weightings must sum to zero. Continuing with this example, to configure the words > nonwords contrast for the analysis specified by the previous call to mkanalysis-sess, you would run the following command within your $SUBJECTS_DIR:
mkcontrast-sess -analysis booth500.sm6.lh -contrast words-v-nonwords -a 2 -a 3 -c 1