The Adoption of Agricultural Technology - Food Security Group

The following example is a simple logistic regression that examines theadoption of a new variety. The dependent variable is variety adoption andthe independent variables are the region of the country, land tenure,cropping practice, and rarmers' age. The variables are listed below:Variety adoption (VAR) o no yesRegion (REG) o forest savannaTenure (TEN) o sharecrop ownerMonocrop (MON) o intercrop monocropAge (AGE)(continLJClus variable)The results of the logistic regression show a highly significant associationwith region, no association with tenure, a significant association withmonocropping, and none with age.Constant -2.087 0.549 -3.803 0.000REG 2.332 0.325 7.169 0.000TEN 0.465 0.400 1.162 0.245MON 1.111 0.310 3.585 0.000AGE -0.012 0.010 -1.289 0.197Sample size 318Log of likelihood function -162.9Chi-square statistic for significance of equation 131.1Degrees of freedom for chi-square statistic 4Significance level for chi-square statistic 0.000Cases correctly predicted 79.0%This example draws on the same datu used in the example on page 73. Inthat example, there was a significant relationship between variety adoptionand tenure. But when we controlled for region, the relationshipdisappeared. The logistic regression does the same thing, and the resultssay that when we control for region (and cropping practice and age) thereis no association between land tenure and varietal a~option.If we were to run the logistic regression without in~luding region, wewould find that tenure appears to have a significant association withvariety adoption (see the follOWing table). The use of multivariatetechniques such as logit models is therefore no guarantee that we willidentify important relationships and discard unimportant ones. The-77