Figure 2
From: Reader technique as a source of variability in determining malaria parasite density by microscopy
Deviation from the mean parasite density decreases as the number of WBCs indexed increases. The residual of each measurement (read of sample Y from microscopist X-mean of all microscopists for sample Y) was scaled by the sample mean and plotted as a function of the number of reference WBCs counted for that read. Reads which were made by indexing RBCs were excluded from this plot, but were included in the sample mean.