Figure 4.2. Relationship between sample size (y) and percentage change
detection for the cable corridor for Shannon and Simpson indices for benthic assemblages.
As an estimated 271.82km2 of the cable corridor remains to be surveyed, a further 36 stations in this area would be required to retain the 2010 survey density of 0.13 stations/km2. This will ensure that the surveys conducted in the remaining areas are spatially consistent with previous work.
4.4 Epibenthic Power Analysis 4.4.1 East Anglia THREE and FOUR.
The results of the Power analysis, for both S and H’ for East Anglia THREE and FOUR, are presented below in Table 4.5.
Table 4.5. Results from Power analysis for East Anglia THREE and FOUR. Effect Size 0.2 0.5 0.8
Power H’ Power S 0.15 0.63 0.95
EA FOUR (n = 6) 0.8
0.99 1
EA THREE ( n = 4) Power H’ 0.11 0.48 0.85
Power S’ 0.57 0.99 1
The Power values from the highest effect size (0.8) are above the required Power threshold (also 0.8). As an es of 0.8 equates to values less than an EDPC of 50%, it is shown that an estimated sample size equal to that carried out during the 2010 survey is sufficiently powerful to detect change of less than 50%. Figure 4.3 also demonstrates this point and therefore that adequate stations have been surveyed.
