Hi Doug, Thanks for confirming how to calculate the 95% confidence interval of the slope for all my clusters. I realized that there was a small error in my formula, in that I should use the critical values from the t-distribution, not the z-distribution (so the SE multiplier will be more like 2.0 instead of 1.96, depending on my sample N).
The problem is that mri_segstats trims the output at the 10,000ths place. Here is the cluster.summary and the segstats from the two clusters identified as significantly associated with age. mc-z.th1.3.neg.sig.cluster.summary: # ClusterNo Max VtxMax Size(mm^2) MNIX MNIY MNIZ CWP CWPLow CWPHi NVtxs Annot 1 -5.096 73213 4275.24 50.0 33.2 -7.2 0.00350 0.00280 0.00430 8455 parstriangularis 2 -3.802 51616 20825.27 4.9 -26.2 39.2 0.00010 0.00000 0.00020 41094 posteriorcingulate gamma.mgh: # ColHeaders Index SegId NVoxels Volume_mm3 StructName Mean StdDev Min Max Range 1 1 8455 8455.0 Seg0001 -0.0089 0.0027 -0.0147 -0.0038 0.0109 2 2 41094 41094.0 Seg0002 -0.0069 0.0017 -0.0132 -0.0023 0.0108 gammavar.mgh: # ColHeaders Index SegId NVoxels Volume_mm3 StructName Mean StdDev Min Max Range 1 1 8455 8455.0 Seg0001 0.0000 0.0000 0.0000 0.0000 0.0000 2 2 41094 41094.0 Seg0002 0.0000 0.0000 0.0000 0.0000 0.0000 So, for the 95% CI of the slope for cluster #1, I would use these formulas (N=60, so the t-distribution 95% critical value is 2.0003): -0.0089+2.0003*sqrt(0.0000) -0.0089-2.0003*sqrt(0.0000) Is there any way to add more significant digits to the mri_segstats output? Thanks, -Kayle On Nov 4, 2013, at 6:31 PM, Douglas N Greve <gr...@nmr.mgh.harvard.edu> wrote: > > Yes, that should work. > doug > > On 10/30/2013 03:35 PM, Kayle Sawyer wrote: >> Hi all, >> >> I would like to calculate the 95% confidence interval of the slope for a >> thickness cluster (vs age in years) produced by mri_glmfit-sim. >> >> I have obtained values for my clusters from gamma.mgh and gammavar.mgh using >> these two commands: >> >> mri_segstats --i gamma.mgh >> --seg mc-z.th1.3.neg.sig.ocn.mgh >> --excludeid 0 >> --sum mc-z.th1.3.neg.sig.ocn.gamma.segstats >> >> mri_segstats --i gammavar.mgh >> --seg mc-z.th1.3.neg.sig.ocn.mgh >> --excludeid 0 >> --sum mc-z.th1.3.neg.sig.ocn.gammavar.segstats >> >> Next, (for each cluster, within each segstats summary file) I would take the >> “mean” from gamma, and the “mean” from gammavar, and calculate the 95% CI >> thus: >> gamma + 1.96*sqrt(gammavar) >> gamma - 1.96*sqrt(gammavar) >> >> Would these two values would give me the 95% confidence interval for the >> effect of age on that cluster, in mm/year? >> >> Thanks, >> -Kayle >> >> ------------------------------------ >> >> Yahoo Groups Links >> >> <*> To visit your group on the web, go to: >> http://groups.yahoo.com/group/martinos-tech/ >> >> <*> Your email settings: >> Individual Email | Traditional >> >> <*> To change settings online go to: >> http://groups.yahoo.com/group/martinos-tech/join >> (Yahoo! ID required) >> >> <*> To change settings via email: >> martinos-tech-dig...@yahoogroups.com >> martinos-tech-fullfeatu...@yahoogroups.com >> >> <*> To unsubscribe from this group, send an email to: >> martinos-tech-unsubscr...@yahoogroups.com >> >> <*> Your use of Yahoo Groups is subject to: >> http://info.yahoo.com/legal/us/yahoo/utos/terms/ >> >> >> > > -- > Douglas N. Greve, Ph.D. > MGH-NMR Center > gr...@nmr.mgh.harvard.edu > Phone Number: 617-724-2358 > Fax: 617-726-7422 > > Bugs: surfer.nmr.mgh.harvard.edu/fswiki/BugReporting > FileDrop: https://gate.nmr.mgh.harvard.edu/filedrop2 > www.nmr.mgh.harvard.edu/facility/filedrop/index.html > Outgoing: ftp://surfer.nmr.mgh.harvard.edu/transfer/outgoing/flat/greve/ > > > > 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 Partners Compliance HelpLine > at > http://www.partners.org/complianceline . If the e-mail was sent to you in > error > but does not contain patient information, please contact the sender and > properly > dispose of the e-mail. > _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
