Table 6.

Number of error responses: unadjusted sample means and adjusted difference in means, for patients with Parkinson’s disease versus patients with essential tremor.

	Unadjusted mean number of error responses		Adjusted difference in mean number of error responses
	PD (N = 63)	ET (N = 53)	$\widehat{\beta }$ a SE	95% CI	P valueb
Phonological fluency
Total errors	2.33	1.96	0.40 0.4	[−0.34, 1.12]	.29
Perseveration errors	1.63	1.20	0.44 0.3	[−0.12, 1.00]	.12
Set-loss errors	0.70	0.75	−0.05 0.2	[−0.45, 0.35]	.81
Category fluency
Total errors	1.11	1.06	0.03 0.3	[−0.49, 0.55]	.92
Perseveration errors	0.90	0.79	0.09 0.2	[−0.35, 0.53]	.69
Set-loss errors	0.21	0.26	−0.06 0.2	[−0.39, 0.26]	.70
Category switching
Total errors	1.15	1.06	0.22 0.3	[−0.36, 0.81]	.45
Perseveration errors	0.49	0.36	0.18 0.1	[−0.08, 0.45]	.17
Set-loss errors	0.67	0.70	0.04 0.3	[−0.40, 0.48]	.86

Note. PD = Parkinson’s disease; ET = Essential Tremor; $\widehat{\beta }$ = coefficient of Diagnosis (PT or ED) term from multivariable regression model t; SE = standard error; CI = confidence interval.

^a$\widehat{\beta }$ represents the difference in mean number of error responses, i.e. mean number of error responses for PD patients – mean number of error responses 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.