Average age is the average of all fish aged. Unageable and
ranged samples were excluded.
Samples may have been collected several years before data was
released.
Rock sole (Lepidopsetta bilineata) statistics are from
samples collected before the species was split into southern rock sole (Lepidopsetta bilineata)
and northern rock sole (Lepidopsetta peracuata).
Precision:Between-reader
precision generally refers to the repeatability of an age when two different
age readers age the same fish, with no knowledge of the other reader's age. For
these twice-aged fish, an age is available from the reader (r) and a more
experienced tester (t).
Three measures of statistical precision can be calculated from the between-reader ages:
1. Percent Agreement (PA):
2. Average Percent Error (APE):
3. Coefficient of Variation (CV):
where n = the number of fish in the test sample and
is
the average age of a single fish.
APE and CV are averaged over all test
samples. Often it is desirable to calculate PA, APE and CV broken down by age
class. This is useful since precision estimates, especially PA, will vary with
age. An advantage of both APE and CV is that they generally will not vary too
much with age as they are scaled by
Kimura, D.K., and J.J. Lyons. 1991. Between-reader bias and variability in the age-determination process. Fish. Bull., U.S. 89:53-60.
is
the average age of a single fish.
