Hi Daniel, there is no difference. Once you select the appropriate
threshold, it does not matter whether it is a z-field, p-field, t-field,
or -log10(p)-field because it gets binarized.
doug
On 9/8/13 9:33 PM, Yang, Daniel wrote:
Hi Doug,
Thanks! I didn't realize that the threshold is a negative exponent to
a base of 10!
Just wondering, is there a webpage that I can read to understand why
FreeSurfer chooses this "exponent" approach instead of z-value?
Also are 1.3, 2.3, 3.3, 4.3 two-sided, and 1, 2, 3, 4, one-sided? For
example, when we specify configure overlay in Freeview?
Thanks!
Daniel
--
Yung-Jui "Daniel" Yang, PhD
Postdoctoral Researcher
Yale Child Study Center
New Haven, CT
(203) 737-5454
On 9/8/13 6:03 PM, "Douglas Greve" <gr...@nmr.mgh.harvard.edu
<mailto:gr...@nmr.mgh.harvard.edu>> wrote:
It is not a z-value. It is -log10(p), so -log10(.01) = 2
doug
On 9/7/13 9:13 PM, Yang, Daniel wrote:
Hi FreeSurfer Experts,
On this page
(https://surfer.nmr.mgh.harvard.edu/fswiki/FsTutorial/QdecMultipleComparisons),
it says: "In particular, thresholds of 1.3, 2, 2.3, 3, 3.3 and 4,
corresponding to p-values of 0.05, 0.01, 0.005, 0.001, 0.0005 and
0.0001, which are common thresholds."
I am wondering how these thresholds were computed.
In my own computation, I found z-value to be the following, but
neither one-sided nor two-sided matches the thresholds of
1.3, …, 4 as shown above?
one-sided:
p-value=0.0500, z-value=1.6
p-value=0.0100, z-value=2.3
p-value=0.0050, z-value=2.6
p-value=0.0010, z-value=3.1
p-value=0.0005, z-value=3.3
p-value=0.0001, z-value=3.7
two-sided:
p-value=0.0500, z-value=2.0
p-value=0.0100, z-value=2.6
p-value=0.0050, z-value=2.8
p-value=0.0010, z-value=3.3
p-value=0.0005, z-value=3.5
p-value=0.0001, z-value=3.9
Thanks!
Daniel
--
Yung-Jui "Daniel" Yang, PhD
Postdoctoral Researcher
Yale Child Study Center
New Haven, CT
(203) 737-5454
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