n = z2Np(1－p) ／ z2p(1－p)＋(N－1)d2
n = Sample size
Z = standard normal score at 95% of confidence interval = 1.96
d = allowance for error = 0.05
N= population size = 7165
p = proportion of high performances of VHVs in elderly care = 0.50
n = 1.96 (7165)(0.5)(0.5) ／ 1.96 (0.5)(0.5) 7164(0.05)2
n = 365
The sample size was increased by 10 % in case there were any incomplete or missing data
during the collection process. The total number of sample size required in this study was at
least 402.