Table 1.

Systematic, random errors and CTV to PTV margin in different directions.

		Error (mm)
Patient No.	No of readings/day	Ant‐Post (z)	Mediolateral (x)	Craniocaudal (y)	Vector Length (r)
1	24	0.45	0.02	$-0.49$	0.78
2	29	$-0.99$	0.20	0.40	1.72
3	26	0.99	0.46	$-0.40$	1.24
4	26	0.29	0.71	0.21	1.06
5	26	$-0.76$	$-0.76$	$-0.23$	1.20
6	24	0.06	0.36	$-0.36$	0.61
7	20	0.16	0.12	0.21	0.62
8	25	0.17	0.17	$-0.42$	0.80
9	27	$-0.07$	0.06	0.26	1.15
10	25	0.08	0.23	$-0.91$	1.19
Population mean error		0.38	0.15	$-0.17$	$1.03\text{SD}=0.34$
Population systematic error (Σ)		0.56	0.38	0.42
Population random error (σ)		1.86	1.36	0.73
CTV to PTV margin (ICRU)		1.86	1.45	0.93
CTV to PTV margin (Stroom)		2.42	1.74	1.35
CTV to PTV margin (Van Herk)		2.7	1.93	1.56
Errors between $+2\text{mm}$ and $-2\hspace{0.17em}\text{mm}$		99.2%	99.6%	97.6%
Errors more than $+2\hspace{0.17em}\text{mm}$ or less than $-2\hspace{0.17em}\text{mm}$		0.8%	0.4%	2.4%

Σ = population systematic error, σ = random error, SD = standard deviation