# comparing dSPMs between conditions with different	numbers of trials

**URL:** <https://mne.discourse.group/t/comparing-dspms-between-conditions-with-different-numbers-of-trials/245>\
**Category:** Mailing List Archive (read-only)\
**Tags:** list-archive\
**Created:** [July 29, 2010, 8:17am UTC](https://mne.discourse.group/t/comparing-dspms-between-conditions-with-different-numbers-of-trials/245 "2010-07-29T08:17:26Z")\
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**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/mne/original/1X/85cc6bd2b69cb698a166dc6d880fb550510d0144.jpeg) [@system](https://mne.discourse.group/u/system)\
**Post date:** [July 29, 2010, 8:17am UTC](https://mne.discourse.group/t/comparing-dspms-between-conditions-with-different-numbers-of-trials/245/1 "2010-07-29T08:17:26Z")

</div>

Dear MNE users,

I have a question about comparing dSPMs between conditions with different  
numbers of trials. I read it from previous messages in the mailing list that  
one should use the same inverse model for different conditions. Does it  
mean to create a inverse model by estimating the noise covariance from all  
trails, and then apply it on different conditions?

In another words, while visualizing the dSPMs in the windows of mne\_analyze,  
can I use the inverse model, which is created by the noise covariance from  
all trails, with a measurement file which is the averaging of part of  
trials? If this is correct, should I keep the value of "nave" as "-1", or  
use the number of all trials instead?

Hope I have made my questions clearly. Thanks.

Chun-Hsien Hsu  
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