Table 3.

Estimation results for inter-shopping-trip durations

	Proportional hazard (fized effects only)
	coef	exp(coef)	z-value	p value
Household size	0.1300	1.139	3.91	0.0001
Age (main shopper)	0.0099	1.010	2.95	0.0032
Basket size (previous shopping occasion)	− 0.0108	0.989	− 10.43	< 2e−16
Online dummy (previous shopping occasion)	− 0.8463	0.429	− 10.22	< 2e−16
Online adopter dummy	0.2103	1.234	2.47	0.0135

	Frailty (mixed effects)
	coef	exp(coef)	z value	p value
Household size	0.1699	1.185	3.66	0.0003
Age (main shopper)	0.0144	1.015	3.26	0.0011
Basket size (previous shopping occasion)	− 0.0056	0.994	− 15.52	< 2e−16
Online dummy (previous shopping occasion)	− 1.0038	0.366	− 21.65	< 2e−16
Online adopter dummy	0.0938	1.098	1.74	0.0820
		95% confidence interval
Random effects: standard deviation	0.639	0.566	0.725

Summary statistics
Number of observations	22815
$\mathcal{L}(0)$	− 142477

		$\mathcal{L}(\widehat{\mathit{\beta }})$	AIC	BIC
Proportional hazard (fixed effects only)		− 141176	282363	282403
Frailty (mixed effects)		− 139480	278972	279020

${}^{\mathrm{a}}$Computed using the profile likelihood method (Therneau 2015)