(a) Period-based sampling plans:
(1) Your cycle of minor schedule changes during a year. For example, quarterly sampling may be appropriate if you routinely adjust your schedule every three months.
(2) The scale of your operation and the method you will be using to select a sample. For example, it may become difficult to select a sample for an entire quarter if the number of service units involved in a quarter is too large for a spreadsheet to handle.
(3) The realized annual sample size. The realized annual sample size can be larger than the initial annual sample size due to rounding in allocating the initial annual sample to each frequency level. This is particularly true for weekly sampling when the initial annual sample size is relatively small. For example, if the initial annual sample size is 55 and you choose weekly sampling, the weekly sample size would be 2 and the realized annual sample size would be 104.
(b) Interval-based sampling plans:
(1) Your staffing needs for data collection.
(2) The number of times you need to do sampling. The number of times is larger with plans of higher frequency (e.g., every vs. every 2nd day).
(3) The annual total sample size. The degree of rounding is higher with plans of higher frequency.