These conflicting views were analyzed using Cochran data (1977, p.
211) [1]. When the population units are ordered, variance of systematic sampling for all possible
systematic samples provides equal, non-negative and most precise estimates for all the variance
functions considered i.e. ( ) ( ) ( ) 12 3 sy sy sy
Vy Vy Vy = = , unlike when a single systematic sample is
used and when variance of simple random sampling is used to estimate selected systematic samples.