biodex BALANCE SYSTEM SD Operation & Service Manual page 85

CONTENTS
The "Score" is defined as the standard deviation of position over the length of the test. The
Standard deviation is interpreted to be the absolute vector length deviation from the mean vec-
tor end point. Basically, all vectors (X,Y) coordinates are summed and divided by the number of
samples, to obtain a vector sum which represents the position of the mean.
N = 1
Xn
sx
N = 0
N = 1
Yn
sy
N = 0
and
N-1 2
φ = sqrt(Σ((Xn-sx)+(Yn-sy) )
n = 0
N
2
— A-3 — APPENDIX A