Table 7.

Mean error rate: unadjusted sample means and adjusted differences in means, for patients with Parkinson’s disease versus patients with essential tremor.

	Unadjusted mean error rate (%)		Adjusted difference in mean percentage of error responses
	PD (N = 63)	ET (N = 53)	$\widehat{\beta }$ a SE	95% CI	P valueb
Phonological fluency
Total errors	5.66	5.55	0.38 1.0	[−1.60, 2.37]	.70
Perseveration errors	3.87	3.30	0.70 0.7	[0.75, 2.15]	.34
Set-loss errors	1.78	2.25	−0.32 0.6	[−1.60, 0.95]	.62
Category fluency
Total errors	3.03	3.02	−0.05 0.8	[−1.67, 1.57]	.95
Perseveration errors	2.27	2.22	−0.04 0.6	[−1.23, 1.14]	.94
Set-loss	0.76	0.79	−0.01 0.6	[−1.20, 1.18]	.99
Category switching
Total errors	8.16	6.89	2.24 1.8	[−1.29, 5.77]	.21
Perseveration errors	3.25	2.48	1.09 0.8	[−0.56, 2.75]	.19
Set-loss errors	4.90	4.74	0.73 1.5	[−2.16, 3.62]	.62

Note. PD = Parkinson’s disease; ET = Essential Tremor; $\widehat{\beta }$ = coefficient of Diagnosis (PT or ED) term from multivariable regression model; SE = standard error; CI = confidence interval.

^a$\widehat{\beta }$ represents the difference in mean percentage of error responses, i.e. mean error % for PD patients – mean error % for ET patients, adjusted for Age, Gender, Years of Education, and Premorbid Intelligence. Statistical inference was based on linear regression with robust variance estimation.

^bNull hypothesis: β = 0.