What assumption do additive models for the sales comparison approach make about the impact of property characteristics upon value?

In additive models for the sales comparison approach, the assumption is that property characteristics are independent of one another regarding their impact on value. This means that the contribution of each individual characteristic—such as square footage, number of bedrooms, or location—can be assessed separately and that the total value of the property is derived from the sum of these individual contributions without one characteristic influencing another.

This independence is crucial for effective analysis because it allows appraisers to isolate the effect of each characteristic on overall property value. By treating these characteristics as independent, appraisers can create more accurate and reliable valuation models. For instance, if an appraiser finds that larger properties typically sell for more, they can independently evaluate how much that size influences value without being influenced by the number of bedrooms, backyard size, or other variables.

The other options suggest different relationships between the characteristics. For instance, if they were dependent, it would indicate that one characteristic might influence the value impact of another, complicating the valuation process. If they were considered residual or negligible, it would imply a lesser or more complicated interaction than what is assumed in an additive model, undermining the simplicity and clarity that is inherent to this approach.