It has no influence on the design matrix. It controls a scaling factor so that the beta value (regression coef) will equal to the height of the hemodynamic response when viewed in the raw data. This sounds like it should be simple but it is actually quite tricky. The bottom line is that it is only a scale factor, so it does not affect p-values or t-values. In your case, I would set it to 1.2s (the mean of your task event durations). doug

On 12/05/2013 11:28 PM, 王晗 wrote:

Hi,

I am making an analysis in freesurfer 5.1 using mkanalysis-sess and I am a bit confused about the flag refeventdur. In the help it is said that it should be set to the event duration if the events have similar durations. But I have two conditions with different durations that one lasts for 1.6 second and another lasts 0.8s in a event-related design paradigm, and my fixation condition lasts for 8 second. What should I set the refeventdur to? How does this value influence the design matrix?

Thanks, WangHan

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