which option is not an estimator variable

Keyword Analysis

Keyword	CPC	PCC	Volume	Score	Length of keyword
which option is not an estimator variable	1.68	0.6	6791	81	41
which	1.17	1	1622	35	5
option	1.21	0.3	5941	44	6
is	1.74	0.4	875	17	2
not	1.42	0.7	221	65	3
an	1.97	0.7	3849	35	2
estimator	1.36	0.1	4713	36	9
variable	1.87	0.5	2630	20	8

Keyword	CPC	PCC	Volume	Score
which option is not an estimator variable	1.88	0.4	2465	76
what is an estimator variable	1.59	0.3	7856	77
estimator must be specified with this option	0.54	0.6	9983	78
estimator vs system variables	1.36	0.2	1930	80
examples of estimator variables	1.21	1	4087	78
estimator variables vs system variables	0.82	1	3238	71
option estimates not allowed	0.17	0.8	6537	74
estimator not a valid estimator	1.97	0.4	934	30
none is not an estimator instance	0.63	0.6	7682	47
system and estimator variables	1.63	0.5	232	18
variable estimate not found	0.75	0.1	4625	24
name estimator is not defined	1.93	1	8896	46
n_estimators are not used	0.05	0.9	9112	71