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King County Department of Assessments

Fair, Equitable, and Understandable Property Valuations

Department of Assessments

500 Fourth Avenue,
Suite ADM-AS-0708,
Seattle, WA 98104

Office Hours:
Mon - Fri
8:30 a.m. to 4:30 p.m.

TEL: 206-296-7300
FAX: 206-296-5107
TTY: 206-296-7888

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Glossary of terms for residential parcels

MARKET AREA
A geographic area, typically encompassing a group of neighborhoods, defined on the basis that the properties within its boundaries are more or less equally subject to a set of one or more economic forces that largely determine the value of the properties in question.

MARKET VALUE
Market value is the major focus of most real property appraisal assignments. Both economic and legal definitions of market value have been developed and refined.

MASS APPRAISAL MODEL
A mathematical expression of how supply and demand factors interact in a market.

MASS APPRAISAL
The process of valuing a group of properties as of a given date, using standard methods, employing common data, and allowing for statistical testing.

MEAN
A measure of central tendency. The result of adding all the values of a variable and dividing by the number of values. For example, the mean of 3,5, and 10 is 18 divided by 3, or six. Also called arithmetic mean.

MEDIAN
A measure of central tendency. The value of the middle term in an uneven number of items arranged or arrayed according to size; the arithmetic average of the two central items in an even number of items similarly arranged; a positional average that is not affected by the size of extreme values. The median of 3,5, and 10 is 5. The middle number.

MODEL CALIBRATION
The development of adjustments, or coefficients based on market analysis, that identifies specific factors with an actual effect on market value.

MODEL SPECIFICATION
The formal development of a model in a statement or equation, based on data analysis and appraisal theory.

MODEL
(1) A representation of how something works. (2) For purposes of appraisal, a representation (in words or an equation) that explains the relationship between value or estimated sale price and variables representing factors of supply and demand.