Do I have to use the switching rules when using the Military Standards?

The proportion of items (or batches, in Skip lot sampling) that are inspected during some phase, when applying continuous sampling. f is between 0 and 1. There are three ways to sample with a fraction of f:

1. Probability Sampling: Each item/batch is sampled with probability f.
2. Systematic Sampling: Every 1/f 'th item/batch is sampled. 1/f must then be a natural number (e.g., every 3rd item is inspected, when f=1/3).
3. Block-Random Sampling: From each 1/f consecutive items/batches, one is chosen at random. 1/f must then be a natural number (e.g., in each block of 3 items one is chosen, whenf=1/3).