The Number of Identified Specimens or Number of Individual Specimens (NISP), is used in archaeology and paleontology when counting bones from a site. NISP counts each bone and fragment as one unit. The NISP is an estimate of the number of individuals at that location.
NISP can often be an overestimate of the actual number of individuals at the site, especially when preservation is good but bones are highly fragmented. Multiple fragments of the same bone lead to it being counted multiple times. However, too much fragmentation can lead to an inability to identify a bone as a particular type in the first place. At many sites with poor preservation the total NISP severely underestimates the total possible number of individuals that contributed to the assemblage. Some paleoindian sites, which often exhibit poor organic preservation, are a case in point. However, this and some other problems can be corrected analytically.
A more serious problem is the one of interdependence. There is generally no reliable way to determine if individually counted specimens originated from the same organism on the ancient landscape and are therefore interdependent. Because this probability can be generally assumed to be >0, NISP in most cases overestimates the actual number of individual animals represented in a recovered assemblage by some unknowable degree.
An alternative estimate to NISP, often done in concert, is minimum number of individuals (MNI). Both are influenced by fragmentation and limited preservation, but in different ways. NISP tends to overestimate the number of individuals under moderate fragmentation, but the overestimate lessens as fragmentation increases due to the inability to classify the bones. MNI tends to underestimate the actual number under medium fragmentation, and even more severely when bones are highly fragmented. Under hypothetically perfect preservation and no fragmentation, these estimates should be the same. MNI also suffers from the aggregation problem, in which different aggregations will generate at least two values, a MNI minimum and maximum, which are generally empirically indistinguishable. Both NISP and MNI are likely only ordinals scale measurements, which means at best they can only give an ordered series of taxonomic abundance, i.e. "Taxon A is more numerous than Taxon B."
NISP should not be used when calculating a sample size for inferential statistics, because it will inflate the statistical significance. Thus in these situations MNI should be used instead.
Famous quotes containing the words number of, number, identified and/or specimens:
“It seems to me that there must be an ecological limit to the number of paper pushers the earth can sustain, and that human civilization will collapse when the number of, say, tax lawyers exceeds the world’s total population of farmers, weavers, fisherpersons, and pediatric nurses.”
—Barbara Ehrenreich (b. 1941)
“There are crimes which become innocent and even glorious through their splendor, number and excess.”
—François, Duc De La Rochefoucauld (1613–1680)
“Linguistically, and hence conceptually, the things in sharpest focus are the things that are public enough to be talked of publicly, common and conspicuous enough to be talked of often, and near enough to sense to be quickly identified and learned by name; it is to these that words apply first and foremost.”
—Willard Van Orman Quine (b. 1908)
“A tattered copy of Johnson’s large Dictionary was a great delight to me, on account of the specimens of English versifications which I found in the Introduction. I learned them as if they were so many poems. I used to keep this old volume close to my pillow; and I amused myself when I awoke in the morning by reciting its jingling contrasts of iambic and trochaic and dactylic metre, and thinking what a charming occupation it must be to “make up” verses.”
—Lucy Larcom (1824–1893)