(1) "Assessment bias" means any tendency or trend of assessment ratios, when analyzed by an appropriate statistical method, which reveals assessment progressivity or assessment regressivity.

(2) "Assessment progressivity" means any systematic pattern of assessment in which higher value properties are generally assessed at a larger percentage of fair market value than properties of lower value.

(3) "Assessment ratio" means the fractional relationship the assessed value of property bears to the fair market value of the property as determined in paragraph (8) of subsection (b) of Code Section 48-5-274.

(4) "Assessment regressivity" means any systematic pattern of assessment in which lower value properties are generally assessed at a larger percentage of fair market value than properties of higher value.

(5) "Assessment variance" means the absolute value of the difference between the assessment ratio for each parcel of property within each class of property and the average assessment ratio for that class and expressed as a percentage of the average assessment ratio.

(6) "Class of property" means any reasonable divisions of homogeneous groups of property that the commissioner determines are necessary to examine digests for uniformity and equalization.

(7) "Digest evaluation cycle" means a recurring period of three years beginning initially on January 1 of the first year, as so designated by the commissioner for each county, and ending on December 31 of the third year thereafter.

(8) "Digest review year" means the first year of each evaluation cycle for each county.