Keyword Analysis & Research: why is history a threat to internal validity

Keyword Analysis

Keyword	CPC	PCC	Volume	Score	Length of keyword
why is history a threat to internal validity	0.43	0.1	3119	69	44
why	0.45	0.2	5961	74	3
is	0.61	0.4	2850	33	2
history	0.52	0.5	9850	73	7
a	0.73	0.5	7343	82	1
threat	0.26	0.3	76	76	6
to	0.22	0.6	1943	77	2
internal	1.84	0.1	4308	79	8
validity	0.43	0.9	1241	73	8

Keyword	CPC	PCC	Volume	Score
why is history a threat to internal validity	0.39	0.5	3846	33