Therefore, in stratified systematic sampling when N nk ≠ , competing methods are: CSS, NPSS, and
RLSS. Due to its greater efficiency over the CSS and NPSS as reported by Chang and Huang (2000) [9], RLSS was used by Kareem et al (2015) [10] in stratum where N nk ≠ . The mean and variance of RLSS is as given below (see relation 2.2 and 2.3, p. 251 of Chang and Huang (2000) [9]).