a. The "average ratio" of assessed to true value of real property for a taxing district for the purposes of this act shall mean that ratio promulgated by the Director of the Division of Taxation pursuant to P.L.1954, c. 86 (C. 54:1-35.1 et seq.), as of October 1 of the year preceding the tax year, as revised by the tax court.
b. The "common level range" for a taxing district is that range which is plus or minus 15% of the average ratio for that district.