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:

- Probability Sampling: Each item/batch is sampled with probability f.
- 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). - 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, when*f*=1/3).