Table 6.

Stepwise regression coefficients, statistical significance, and collinearity assessment.

Model and predictors			Unstandardized coefficients				Standardized coefficients (β)		t value (df)		P value		95% CI for B		Collinearity statistics
			B		SE										Tolerance		VIFa
1
	Constant	2.241		0.103		N/Ab		21.849 (79)		<.001		2.036 to 2.445		N/A		N/A
	Length	0.006		0.001		0.534		5.618 (79)		<.001		0.004 to 0.008		1.000		1.000
2
	Constant	2.779		0.146		N/A		19.087 (78)		<.001		2.489 to 3.069		N/A		N/A
	Length	0.005		0.001		0.464		5.412 (78)		<.001		0.003 to 0.007		0.970		1.031
	Content	–0.286		0.060		–0.406		–4.738 (78)		<.001		–0.407 to –0.166		0.970		1.031
3
	Constant	3.230		0.207		N/A		15.618 (77)		<.001		2.818 to 3.642		N/A		N/A
	Length	0.005		0.001		0.457		5.586 (77)		<.001		0.003 to 0.006		0.969		1.032
	Content	–0.294		0.058		–0.416		–5.089 (77)		<.001		–0.409 to –0.179		0.968		1.033
	Physicians	–0.274		0.093		–0.237		–2.943 (77)		.004		–0.459 to –0.089		0.998		1.002

^aVIF: variance inflation factor.

^bN/A: not applicable.