. Author manuscript; available in PMC: 2014 Mar 25.

Published in final edited form as: Health Econ. 2009 Dec;18(12):1420–1439. doi: 10.1002/hec.1437

Table 4.

Preferences for Canadian and US General Population and Physician Respondents - Bivariate Probit Regression model results

Attribute	Level	Canadian General Population		US General Population		Canadian Physicians		US Physicians
Attribute	Level	parameter estimate	SE	parameter estimate	SE	parameter estimate	SE	parameter estimate	SE
	# observations	9,988		21,142		2,200		2,178
	# respondents	454		961		100		99

Process	stool	0.0357		0.1543	^***	0.0903		0.1591	^*
	scope	-0.1145	^***	-0.1414	^***	0.0240		0.0548
	barium enema	-0.1704	^***	-0.2208	^***	-0.1496	^*	-0.3510	^***
	CT^†	0.2492	^***	0.2079	^***	0.0353		0.1371	^*

Frequency	once	0.1019	^**	0.0589	^*	0.3585	^***	0.1674	^*
	q 10 yr	-0.0518		-0.0381		0.0422		0.1831	^**
	q 5 yr	0.0357		0.0531		-0.1371		-0.0630
	annual^†	-0.0858	^**	-0.0739	^***	-0.2636	^***	-0.2875	^***

Follow-up	none	0.0118		0.0080		0.0279		0.0148
Follow-up	yes^†	-0.0118		-0.0080		-0.0279		-0.0148

Pain	none	0.1830	^***	0.1925	^***	0.1667	^***	0.2293	^***
	mild	-0.2603	^***	-0.2788	^***	-0.3210	^***	-0.2976	^***
	sedative^†	0.0773	^***	0.0863	^***	0.1543	^***	0.0683

Preparation	diet	-0.0393		-0.0606	^*	-0.1373		-0.0525
	laxative	-0.0879	^*	-0.0420		-0.1016		-0.2632	^**
	enema	-0.0198		-0.0548	^**	0.0513		0.0811
	none^†	0.1470	^***	0.1574	^***	0.1876	^**	0.2346	^***

Complication risk	none	0.1572	^***	0.1481	^***	0.1448	^*	0.0767
	1/1000 to 1/10000	0.0464	^*	0.0902	^***	0.0744		0.1439	^**
	1/100^†	-0.2036	^***	-0.2383	^***	-0.2192	^***	-0.2206	^***

Specificity	90%	0.2161	^***	0.1781	^***	0.3305	^***	0.2070	^***
	80%	0.0364		0.0700	^***	0.1627	^**	0.1421	^*
	50%^†	-0.2525	^***	-0.2481	^***	-0.4932	^***	-0.3491	^***

Sensitivity	90%	0.3071	^***	0.3170	^***	0.5448	^***	0.3916	^***
	70%	0.0167		0.0421	^*	0.0920		0.0564
	40%^†	-0.3238	^***	-0.3591	^***	-0.6368	^***	-0.4480	^***

	cost constant	-0.0010	^***	-0.0010	^***	-0.0019	^***	-0.0018	^***

marginal utility of money		0.0085		0.0095		0.0134		0.0199
	NO TEST	-0.9087	^**	-0.4592	^***	0.1801		-0.1886
	ln(LAM)	0.8482	^**	0.9289	^***	0.4486	^**	0.4296	^**

	Personal characteristic interactions
	male	-0.1570		-0.3247	^***
	income^‡	-0.3849	^*	-0.5944	^***
	age 51-60 years	-0.0444		-0.1097
	age > 60 years	-0.4343	^*	-0.5039	^***

	Physician characteristic interactions
	experience (y)					0.0199	^*	0.0162	^*
	n pts >50 y/wk					-0.0068	^**	-0.0041

Model goodness of fit statistics
-2 Log likelihood, full model:		12005.42		25376.52		2436.10		2521.93
-2 Log likelihood, restricted model:		12794.07		27710.83		3003.14		2983.58
likelihood ratio χ²		788.64	^**	2334.31	^**	567.04	^**	461.65	^**
degrees of freedom		24		24		22		22
Maddala’s pseudo-R²		0.1461		0.1981		0.4028		0.3455
McFadden’s pseudo-R²		0.0616		0.0842		0.1888		0.1547
Craig & Uhler’s pseudo-R²		0.2724		0.3589		0.6461		0.5741

SE = standard error;

= p<0.05,

^**

= p<0.01,

^***

= p<0.001

^†

calculated as the negative sum of the parameter estimates of all other levels for the same attribute

^‡

$ CDN for CDN general population and $ US for US general population