The data in table 8.3 are for a small artificial population that exhibits a fairly steady rising trend. We have N=40, K=10,n=4. Each column represents a systematic sample, and the rows are the strata. The example illustrates the situation in which the “within-stratum” correlation is positive. For instance, in the first five systematic samples. In the last five samples, deviations from the strata means are mostly positive. Thus the cross-product terms in ᵨ are predominantly positive. From theorem 8.3 we expect systematic sampling to be less precise than stratified random sampling with one unit per stratum.