Z-score tPAC of multiple trials

Discussions
1

Hi Francois

I have done tPAC calculating on multiple trials for one condition, and want to get the averaged z-score result, so that I can compare the result with that of another condition. I am wondering which pipeline is appropriate:
① Z-score using surrogate for each trial, and then average the z-scored result across trials.
② Average the tPAC results of trials and surrogate data across trials, and then z-score using averaged surrogate data.

Could you give me an advise? Thank you.

2

@Samiee @Sylvain?

3

I would go with the first option, but @Sylvain may provide more insightful suggestions.

4

If you average z-scores across trials, the outcome is not interpretable as a z-score anymore, right?
It depends on the reference mean and std you pick and the rationale behind standardizing with z-scores. What are they in your case?

5

Thanks Samiee and Sylvain.
As for z-score, I generate the surrogate data for each trial following the recommendations in this paper (Aru, J. 2015), and intend to calculate z-score using the mean and std of the surrogate database.
In your opinion, which option is more rational in this case?

6

Then I would recommend you z-score the average of tPAC across trials based on the mean and std observed across surrogates.

7

Many thanks for your reply.
If I understand correctly, you recommend to analyze as the following procedures:

  1. To calculate tPAC for each trial, and then get the average tPAC of all trials.
  2. For each trial, to calculate tPAC of multiple surrogates (100 times), and get the mean and std across surrogates.
  3. To average the surrogate mean and std of all trials.
  4. Z-score the average tPAC based on the result from step 3.
    Did I get it right?
8

Correct.
You may also want to refer to the following paper for more practical guidelines:

https://www.frontiersin.org/articles/10.3389/fncom.2018.00026/full

9

Thank you so much.

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