Closed yossy-biomech closed 4 years ago
This means that identical values appears in all observations. Usually this happens when there is a time node that has a value of zero in all observations.
To check, try computing the standard deviation of the pairwise differences:
d = yA - yB # pairwise differences
sd = d.std(axis=0, ddof=1) # standard deviation of the pairwise differences
print( sd )
You will likely see one or more nan
values, implying that these are zero-variance nodes.
It is not possible to conduct statistical inference parametrically when there is zero variance.
When paired t-test was used, following message was appeared.
"Zero variance detected at the following nodes:"
13 pariticipants were attended.
The participants did movements in two conditions.
When the movements in two conditions are nearly same, is the message appeared?