. 2010 Apr 9;50(5):681–693. doi: 10.1093/geront/gnq028

Table 4.

Bivariate Tobit Estimates of the Effects of ADL and IADL Disability Changes on Changes in the Monthly Hours of Care Received by Husbands and Wives, Health and Retirement Study 2000–2002^a

	Husbands				Wives
	Change in spousal hours		Change in nonspousal hours		Change in spousal hours		Change in nonspousal hours
Outcome variable	Coefficient (SE)	χ² for test of symmetry^b	Coefficient (SE)	χ² for test of symmetry^b	Coefficient (SE)	χ² for test of symmetry^b	Coefficient (SE)	χ² for test of symmetry^b
Change in ADL (ref. no change)
Increase in ADL	156.1** (32.7)	2.36	105.2** (32.4)	1.48	−1.2 (33.9)	8.55**	30.3 (27.8)	1.04
Decrease in ADL	−77.7** (30.9)	2.36	−43.4 (31.5)	1.48	−164.8** (34.4)	8.55**	−78.8** (29.2)	1.04
Change in IADL (ref. no change)
Increase in IADL	179.4** (31.7)	0.34	94.2** (30.7)	0.16	106.6** (33.7)	0.25	83.9** (27.6)	0.59
Decrease in IADL	−149.1** (34.8)	0.34	−73.4* (36.3)	0.16	−79.3* (37.1)	0.25	−48.4 (31.8)	0.59

Notes: ADL = activities of daily living; IADL = instrumental activities of daily living.

The bivariate Tobit models were estimated separately for husbands and wives and include all control variables (see Table 5 for other variable coefficients); changes in disability and in care hours were measured between 2000 and 2002.

Wald tests for H₀: α = −β, where α is the coefficient associated with an increase in ADL or IADL disability and β is the coefficient associated with a decrease in ADL or IADL disability_; chi-square statistics are reported (1 df). †p ≤ .10. *p ≤ .05. **p ≤ .01 (two tailed).