. 2016 May 25;18(5):e100. doi: 10.2196/jmir.5145

Table 5.

Correlations between the three readability indexes and length.

Variable	SMOG grade		Flesch-Kincaid grade level		Szigriszt’s perspicuity index		Length
	r²	P^a	r²	P^a	r²	P^a	r²	P^a
SMOG grade	—	—	.92	<.001	.81	<.001	.05	<.001
Flesch-Kincaid grade level	—	—	—	—	.95	<.001	.03	<.001
Szigriszt’s perspicuity index	—	—	—	—	—	—	.02	.003

^a ANOVA.