. Author manuscript; available in PMC: 2015 Sep 1.

Published in final edited form as: J Neuropathol Exp Neurol. 2014 Sep;73(9):880–890. doi: 10.1097/NEN.0000000000000107

Table 2. Coefficients of variation and average coefficients of error for suicide and non-suicide deaths in dorsal and ventral white matter.

		Activated Phagocytes			Resting Microglia			Perivascular Cells
Region	Suicide	CV	CE	$\sqrt{C V^{2} - C E^{2}}$	CV	CE	$\sqrt{C V^{2} - C E^{2}}$	CV	CE	$\sqrt{C V^{2} - C E^{2}}$
Dorsal	no	0.42	0.07	0.41	0.45	0.08	0.44	0.23	0.08	0.22
Dorsal	yes	0.46	0.07	0.45	0.36	0.07	0.35	0.19	0.07	0.18
Ventral	no	0.52	0.10	0.51	0.36	0.09	0.35	0.27	0.09	0.25
Ventral	yes	0.34	0.07	0.33	0.34	0.07	0.33	0.23	0.08	0.22

CV, coefficient of variation (group standard deviation/group mean), CE, coefficient of error (root mean square of theoretical coefficients of error for each case in group).

The normalized variance for each measure within each group (suicide and non-suicide), CV², contains a contribution, CE², from the error introduced into each measurement by counting systematic random samples rather than counting all of the cells of a given type, plus a contribution, CV²-CE², from the true variation among cases in the group. Thus, the minimum CV that can be obtained by counting more cells per subject is $\sqrt{C V^{2} - C E^{2}}$ . Any further reduction in the uncertainty of the mean ( $normalized standard error = CV ∕ \sqrt{N - 1}$ ) can be achieved only by increasing N, the number of subjects in the group.