Although tables can provide a useful guide for
determining the sample size, you may need to
calculate the necessary sample size for a different
combination of levels of precision, confidence, and
variability. The fourth approach to determining
sample size is the application of one of several
formulas (Equation 5 was used to calculate the
sample sizes in Table 1 and Table 2).interviews planned (this number is often increased to
compensate for nonresponse). Second, the sample
sizes in Table 2 presume that the attributes being
measured are distributed normally or nearly so. If
this assumption cannot be met, then the entire
population may need to be surveyed