. 2019 Jul 16;99(10):1381–1393. doi: 10.1093/ptj/pzz091

Table 2.

Correlation Coefficients^a for Relationship Between RPD Scales^b and Logarithm^c of RMS of Postural Sway Measures for Each Study Group^d

		Correlation Coefficients for the Postural Sway Measures
Scale	Group (Age, y)	RMS of Pitch Displacement	RMS of Roll Displacement	RMS of Pitch Velocity	RMS of Roll Velocity	RMS of AP Acceleration	RMS of ML Acceleration
Numerical	Young (18–44)	0.66	0.83	0.54	0.80	0.69	0.82
	Middle-aged (45–59)	0.77	0.87	0.63	0.81	0.76	0.85
	Old (60–74)	0.74	0.87	0.58	0.76	0.69	0.81
	Very old (75–85)	0.72	0.86	0.68	0.82	0.72	0.82
	All (18–85)	0.73	0.86	0.60	0.80	0.71	0.82
Qualitative	Young (18–44)	0.63	0.77	0.48	0.74	0.63	0.75
	Middle–aged (45–59)	0.74	0.84	0.58	0.78	0.73	0.81
	Old (60–74)	0.74	0.88	0.56	0.76	0.69	0.81
	Very old (75–85)	0.73	0.84	0.68	0.79	0.72	0.79
	All (18–85)	0.71	0.84	0.57	0.76	0.69	0.79

^{^a}

^aCorrelation = √[sum of squares for postural measure/(sum of squares for postural measure + sum of squares for residual)].⁴⁴

^{^b}

^bNumerical and qualitative.

^{^c}

^cBase 10.

^{^d}

^dAll correlation coefficients were significant at P < .001. AP = anteroposterior; ML = mediolateral; RMS = root–mean–square; RPD = ratings of perceived difficulty.