Design and Usability of a Home Telerehabilitation System to Train ...

Table 1: Performance scores
T = target trajectory, X = response trajectory, N = number of data points in record
Metric and Name Computation Algorithm Interpretation
E = Total Error = RMS Error
1 / 2
⎛ 1
2 ⎞
⎜ ∑( X i − Ti
) ⎟
⎝ N
⎠
RMS error between response and
target.
CE = Constant Error = Average
Error
1
∑( X i − Ti
)
N
Average error between response
and target. Reveals bias above or
below target.
VE = Variable Error = Standard
Deviation
1/
2
⎛ 1
2 ⎞
⎜ ∑(
X i − Ti
− CE)
⎟
⎝ N
⎠
Standard deviation of the
response about the bias. Measure
the spread of the response.
CE/VE CE / VE
>1 for response far from target
but consistent, 0 means response lags target.
Fade (First half RMS)/(Last half RMS) > 1 means response getting
smaller as trial proceeds.
Frequency (Zero crossings of
Large score means subject has
response)/(Zero crossings of
target)
tremor.
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