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This sample floor plan of a one-story library demonstrates some of the problems in sampling from a library's stacks. Goal of the surveyor is to assign a unique number to each possible shelving location in the library, with each location having an equal chance of being selected for sampling. Not all ranges contain the same number of bays, and not each bay contains the same number of shelves. The number of books or items can vary greatly from one shelf to the next. Thus, two kinds of failure in sampling are 1) unrecorded locations 2) and empty locations. When completing the random sample form, you must estimate each value (floor, range, bay, shelves, books) large enough not to systematically exclude certain locations, resulting in unrecorded locations.

To reduce the number of empty locations, on the floorplan combine shelving units into equal sizes. In this library the surveyor has accommodated variations in shelving pattern by defining certain shelving units as "ranges" in order to equalize the number of items in each range. For example, Range 1 consists of 43 bays, each of which is only 3 shelves high. The "standard range" in this library is 20 bays, each of which is 7 shelves high, e.g., Ranges 2-6. Range 17 is compiled form a number of low shelving units, similar to range 1. Likewise, Range 16 is a combination of several short ranges.

The surveyor will fill out the Calipr random number default screen this way: