Assessment Of Confidence In The Data - Planet WGSW-24010 User Manual

5.3

Assessment of confidence in the data

The MTR score is suffixed by the three measures of confidence assigned based on site
comparability (I, II, III: see 4.6.12), survey conditions/typicality (A, B, C: see 4.5.7) and the
number of highlighted taxa (a, b, c: see 5.2), to enable an immediate interpretation of likely
confidence in the data.
For example: U/S
D/S
Thus, it is clear that both sites are physically comparable; that site survey accuracy at the
upstream site was affected to a moderate degree by some management, adverse turbidity or the
like, but not at the downstream site; and that 5–8 highlighted taxa were recorded.
It is strongly recommended that surveys with a suffix of confidence of 'III' and/or 'C' should not
be used for interpretation of trophic status, as there is sufficient cause for concern that either the
MTR does not represent the prevailing trophic status at the site and/or any differences in MTR
between sites may be due to factors other than a difference in trophic status. In such cases, effort
should be made to look for and survey an alternative site or pair of sites. To minimise this
circumstance, care should be taken both in the initial selection of the survey lengths, to avoid
selection of unsuitable lengths (see Box 2), but also upon arrival at site for established survey
lengths, to confirm that MTR is an appropriate method to use (see Box 3).
R&D Technical Report E38
MTR = 43.0 (I, B, b)
MTR = 14.7 (I, A, b)
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