What connects a ratio study to the evaluation of model performance?
Correct Answer
D) It compares modelled values against actual prices
A sales-ratio study compares assessed or modeled values with suitable verified sale prices on a consistent basis, including appropriate treatment of valuation and sale dates. The ratios help evaluate valuation level and uniformity across the sample and relevant strata. Results depend on representative sales and sound validation; good aggregate statistics do not guarantee that every individual estimate is accurate. Selectively changing only sold properties can distort the study.
Why This Is the Correct Answer
Option D is correct because a ratio study compares modeled values against actual sale prices. The ratios show whether the model's values are at an appropriate level and how uniform they are across the sample and relevant groups, which is why USPAP names appraisal-to-sale ratio studies as a model performance technique.
Why the Other Options Are Wrong
Option A: It confirms the model vendor's licensing status
Option A says a ratio study confirms the model vendor's licensing status. A ratio study measures how well values compare with sale prices, not anything about a vendor's licensing.
Option B: It replaces the need for random sample testing
Option B says a ratio study replaces the need for random sample testing. A ratio study is one testing technique; it does not eliminate other testing and review that may be required.
Option C: It sets the confidence score for each estimate
Option C says a ratio study sets the confidence score for each estimate. Ratio studies evaluate performance across a group of sales, while confidence scores are model- or vendor-defined indicators for individual estimates.
Ratio equals model over market
A ratio study divides the model's value by the market's price, so it directly tests how close the model comes to reality.
How to use: Use this formula to recall what a ratio study measures.
Exam Tip
Ratio study questions usually point to comparing values with sale prices to test level and uniformity.
Common Mistakes to Avoid
- -Thinking a good ratio study proves each individual estimate is accurate
- -Selectively changing only sold properties, which distorts the study
- -Confusing ratio studies with vendor confidence scores
Concept Deep Dive
Analysis
This question tests the purpose of a ratio study in judging model performance. A ratio study compares modeled or assessed values with verified sale prices, and the resulting ratios measure valuation level and uniformity. USPAP lists appraisal-to-sale ratio studies among the techniques for evaluating model performance.
Background Knowledge
In mass appraisal, a sales-ratio study divides each modeled or assessed value by a verified sale price on a consistent basis, including appropriate treatment of dates. Statistics on the ratios measure level and uniformity. Good aggregate results depend on representative sales and do not guarantee that each individual estimate is accurate.
Real-World Application
An assessor tests a new model by dividing modeled values by verified sale prices for recent sales. The median ratio is close to one overall, but one neighborhood shows consistently low ratios, prompting a model review for that area.
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