Compare the formula to calculate the computed precision interval for ratio estimation (Figure 6-3) to the one for difference estimation (Figure 5-4). In what way are they different ?

where: N CPI N.Z.SD = CPI = computed precision interval N = population size Z = confidence coefficient (two-sided) for CL desired SD = estimated population standard deviation n = sample size finite correction factor FIGURE 6-3 The computed precision interval at the desired con- fidence level