External Email - Use Caution
Dear FreeSurfer experts,
I have two groups and two time points and I would like to do a correlation analysis between a variable (cognition) and the change score in cortical thickness between the two time points (time2 minus time1).
I would like to see if the *correlation *is *different *among each group, if there is an interaction with the group.
I have followed the paired t test instructions ( https://secure-web.cisco.com/11YHUupGYyGBe5w6QAQb3OOLcNluK0Tqv4VUmAmDx5wuogv...), but I am not sure about the contrast(s) I have to use.
The paired-diff.fsgd file (second fsgd file) is the following:
GroupDescriptorFile 1 Title OSGM Class Group1 Class Group2 Variables cognition Input subject1pair Group1 0.546 Input subject1pair Group2 -0.243 ...
How should it be the contrasts files to see the *correlation *of the variable cognition with the change score in thickness taking into account the groups? And should I use DODS or DOSS?
Using DODS: 0 0 0.5 0.5 or 0 0 1 -1
I don't understand the difference between both contrasts. I think I should use the one of "0 0 1 -1" to see whether the cognition variable correlates with change in thickness differently according to the group. Is this correct?
Using DOSS: 0 0 1
Thank you very much in advance.
Kind regards,
Agurne
If you are looking for the difference in the correlation between the groups then you have to use DODS and 0 0 1 -1. The way to understand it is that you have four regression coefficients and each means something. The way you have it set up in the fsgd file is that they are 1. group 1 intercept 2. group 2 intercept 3. group 1 cognition slope 4. group 2 coginition slope Each coefficient gets multipled by its corresponding weight in the contrast and then the results are summed. So if you use 0 0 1 -1 you end up with contrast = g1cogslope-g2cogslope which is the difference you want
If you are just interested in whether the cog slope changes without regard to the group, then you would use 0 0 0.5 0.5 which means contrast = 0.5*g1cogslope + 0.5*g2cogslope which is the average of the slopes. In this case, using DOSS and 0 0 1 will give you the same results if there is no difference in the cog slopes between the groups
On 1/12/2023 8:48 AM, Agurne Sampedro Calvete wrote:
External Email - Use Caution
Dear FreeSurfer experts,
I have two groups and two time points and I would like to do a correlation analysis between a variable (cognition) and the change score in cortical thickness between the two time points (time2 minus time1).
I would like to see if the *correlation *is *different *among each group, if there is an interaction with the group.
I have followed the paired t test instructions (*MailScanner has detected a possible fraud attempt from "secure-web.cisco.com" claiming to be* https://surfer.nmr.mgh.harvard.edu/fswiki/PairedAnalysis https://secure-web.cisco.com/11YHUupGYyGBe5w6QAQb3OOLcNluK0Tqv4VUmAmDx5wuogvWlaypoD3OpvEWBM2c4Wa29T38k5k4_bq_JXA-kc8P0mACbCulAMmVSDKvC4Tl7x6Gk2A_azFExScL0y5HFngabH5bZRoIDy_dKvAtXkXegvTr-2ftNMkD3TQlTwaQtCSI-0554BriqrUu1MKXy2ZDf8l6cSP5im59p93FqJma0yYa3cYXujDp-aXCIOKlUXzojlgBIskwrWMiPG0pmIn08tOj1OYgSExrdJrOrWu2iAIGdhvSK3iuWEQ7BCEp4De-DPfIldNoZfbygVQ1mrt9CvPacDWwenDkjC7Q40A/https%3A%2F%2Fsurfer.nmr.mgh.harvard.edu%2Ffswiki%2FPairedAnalysis), but I am not sure about the contrast(s) I have to use.
The paired-diff.fsgd file (second fsgd file) is the following:
GroupDescriptorFile 1 Title OSGM Class Group1 Class Group2 Variables cognition Input subject1pair Group1 0.546 Input subject1pair Group2 -0.243 ...
How should it be the contrasts files to see the *correlation *of the variable cognition with the change score in thickness taking into account the groups? And should I use DODS or DOSS?
Using DODS: 0 0 0.5 0.5 or 0 0 1 -1
I don't understand the difference between both contrasts. I think I should use the one of "0 0 1 -1" to see whether the cognition variable correlates with change in thickness differently according to the group. Is this correct?
Using DOSS: 0 0 1
Thank you very much in advance.
Kind regards,
Agurne
Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
External Email - Use Caution
Thank you very much for your rapid response. Best regards,
*-- --*
*Agurne Sampedro Calvete, PhD*
Departamento de Psicología / Psikologia Saila / Department of Psychology Facultad de Ciencias de la Salud / Osasun Zientzien Fakultatea / Faculty of Health Sciences Neuropsychology of Severe Medical Conditions Research Team - Neurolab http://secure-web.cisco.com/1gsFGeZNf08M2NUekGr8282Ehtf620Mb3MaIqgn4S6h30847...
Universidad de Deusto / Deustuko Unibertsitatea/ University of Deusto Avda de las Universidades 24, 48007, Bilbao (Spain) Phone: +34 94 413 90 00 (ext 3015) Office: https://secure-web.cisco.com/1V1rBfZ8JjCamegLyFj5UeLkH2vv3nZmVOnRrIltvzrumik...
El jue, 12 ene 2023 a las 15:47, Douglas N. Greve (dgreve@mgh.harvard.edu) escribió:
If you are looking for the difference in the correlation between the groups then you have to use DODS and 0 0 1 -1. The way to understand it is that you have four regression coefficients and each means something. The way you have it set up in the fsgd file is that they are
- group 1 intercept
- group 2 intercept
- group 1 cognition slope
- group 2 coginition slope
Each coefficient gets multipled by its corresponding weight in the contrast and then the results are summed. So if you use 0 0 1 -1 you end up with contrast = g1cogslope-g2cogslope which is the difference you want
If you are just interested in whether the cog slope changes without regard to the group, then you would use 0 0 0.5 0.5 which means contrast = 0.5*g1cogslope + 0.5*g2cogslope which is the average of the slopes. In this case, using DOSS and 0 0 1 will give you the same results if there is no difference in the cog slopes between the groups
On 1/12/2023 8:48 AM, Agurne Sampedro Calvete wrote:
External Email - Use CautionDear FreeSurfer experts,
I have two groups and two time points and I would like to do a correlation analysis between a variable (cognition) and the change score in cortical thickness between the two time points (time2 minus time1).
I would like to see if the *correlation *is *different *among each group, if there is an interaction with the group.
I have followed the paired t test instructions (*MailScanner has detected a possible fraud attempt from "secure-web.cisco.com" claiming to be* https://secure-web.cisco.com/1fXRzP-yKkgu2fox62nZ66JPTjq0Td7zmK1ZioRYjE3sOtW... https://secure-web.cisco.com/11YHUupGYyGBe5w6QAQb3OOLcNluK0Tqv4VUmAmDx5wuogvWlaypoD3OpvEWBM2c4Wa29T38k5k4_bq_JXA-kc8P0mACbCulAMmVSDKvC4Tl7x6Gk2A_azFExScL0y5HFngabH5bZRoIDy_dKvAtXkXegvTr-2ftNMkD3TQlTwaQtCSI-0554BriqrUu1MKXy2ZDf8l6cSP5im59p93FqJma0yYa3cYXujDp-aXCIOKlUXzojlgBIskwrWMiPG0pmIn08tOj1OYgSExrdJrOrWu2iAIGdhvSK3iuWEQ7BCEp4De-DPfIldNoZfbygVQ1mrt9CvPacDWwenDkjC7Q40A/https%3A%2F%2Fsurfer.nmr.mgh.harvard.edu%2Ffswiki%2FPairedAnalysis), but I am not sure about the contrast(s) I have to use.
The paired-diff.fsgd file (second fsgd file) is the following:
GroupDescriptorFile 1 Title OSGM Class Group1 Class Group2 Variables cognition Input subject1pair Group1 0.546 Input subject1pair Group2 -0.243 ...
How should it be the contrasts files to see the *correlation *of the variable cognition with the change score in thickness taking into account the groups? And should I use DODS or DOSS?
Using DODS: 0 0 0.5 0.5 or 0 0 1 -1
I don't understand the difference between both contrasts. I think I should use the one of "0 0 1 -1" to see whether the cognition variable correlates with change in thickness differently according to the group. Is this correct?
Using DOSS: 0 0 1
Thank you very much in advance.
Kind regards,
Agurne
Freesurfer mailing listFreesurfer@nmr.mgh.harvard.eduhttps://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://secure-web.cisco.com/17hOYyhnWlmhUAGHlnglcF9a5UvcMJio0pZlqei1b46OPBA... The information in this e-mail is intended only for the person to whom it is addressed. If you believe this e-mail was sent to you in error and the e-mail contains patient information, please contact the Mass General Brigham Compliance HelpLine at https://secure-web.cisco.com/1HkdOhS-9Wl8WBJw_Y6rsIa8Y6MseKpcGiglMhUOo7YeaTV... < https://secure-web.cisco.com/1HkdOhS-9Wl8WBJw_Y6rsIa8Y6MseKpcGiglMhUOo7YeaTV... . Please note that this e-mail is not secure (encrypted). If you do not wish to continue communication over unencrypted e-mail, please notify the sender of this message immediately. Continuing to send or respond to e-mail after receiving this message means you understand and accept this risk and wish to continue to communicate over unencrypted e-mail.
freesurfer@nmr.mgh.harvard.edu
-
Agurne Sampedro Calvete -
Douglas N. Greve