Table 4.

Post-hoc analysis of number of correct responses, including adjustment for processing speed.

	Parkinson’s disease (N = 63)		Essential tremor (N = 53)
	Mean	SD	Mean	SD	P valueb	Effect Size
Processing speed Composite (Z-score)a	0.2	0.7	0.5	0.6	0.03	0.41
	Adjusted difference in mean number of correct responses
	$\widehat{\beta }$c SE	95% CI	P valueb
Phonological fluency	4.0 2.0	[0.1, 7.9]	.04
Category fluency	2.4 1.7	[−0.4, 5.2]	.09
Category switching	0.0 0.5	[−1.0, 1.0]	.99

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

^aProcessing speed composite score includes the following test measures: SDMT, Oral, DKEFS Color Word, Word. For a normative sample, a Z-score mean is 0 and standard deviation (SD) is 1.

^bNull hypothesis: β = 0.

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

Signifiant levels are bolded.