Correction to: Cerebellar transcranial direct current stimulation in spinocerebellar ataxia type 3 (SCA3-tDCS): rationale and protocol of a randomized, double-blind, sham-controlled study (BMC Neurology, (2019), 19, 1, (149), 10.1186/s12883-019-1379-2)

Abstract

Following publication of the original article [1], the authors noticed an error in the power calculation. The reported power of 0.83 was based on an effect size of 0.46 rather than a partial η2 value of 0.46. Using a partial η2 value of 0.46, which corresponds to an effect size f of 0.92, and five repeated measurements in 20 participants would yield a power of 0.999. The original sentence “Based on the data presented in the aforementioned study, a calculation (G*Power 3) revealed a power of 83% to detect significant differences when using SARA as the primary outcome measure (effect size 0.46, α = 0.05, sample size 20)” is therefore replaced as follows: “Based on the reported partial η2 value of 0.46 in the aforementioned study, which corresponds to an effect size f of 0.92, a sample size of 20 participants who each have five measurements would yield an estimated power of 0.999 (G*Power 3.1) to detect significant differences when using SARA as the primary outcome measure (α = 0.05).” The original article has been corrected.