Keep the two abundance measures apart and scale each correctly. Frequency of occurrence is the fraction of quadrats in which a species appears (its numbers are irrelevant); density is the mean count per quadrat scaled to the whole area by (total area divided by quadrat area). Any estimate is valid only from a random, representative sample.
Trigger: quadrat, transect or kite-diagram data with options that mix fractions, per-square-metre values and totals.
Instances:
(i) frequency equals quadrats containing the species divided by quadrats sampled; a distractor equal to a mean or a total count is a density, not a frequency;
(ii) density in the field equals the mean per quadrat times (area divided by quadrat area); convert the quadrat side to metres first (a 0.5 m side gives 0.25 m2);
(iii) reject any scaling from a biased sample (all sweeps at the edge) or any 'always' claim about quadrat size, since random quadrats vary and a small quadrat is only usually, not always, less likely to contain the species;
(iv) read a kite diagram by the width of its shading (wider means more individuals) and count overlapping kites to find the richest sampling point.
