(a) The initial results of the sample estimate are analyzed in accordance with the following procedures. If the coefficient of variation is larger than a predetermined value, a supplemental sample is required. For purposes of this section, initial results shall mean the determinations of a coefficient of variation and supplemental sample as computed from the original survey data, regardless of the first use of the survey data, except that data changes subsequent to the original determinations that are incorporated into the survey data prior to, but not at the same time as, completion of the supplemental sample have the following effect:

1. (1) If the municipality, borough of New York City, segment in a segment survey assessing unit, class in a special assessing unit or homestead assessing unit, school district designated in former 9 NYCRR section 186-6.1, as repealed in 1998 and set forth in section 1230 of the Real Property Tax Law, or class in a portion in a special assessing unit or homestead assessing unit:

   1. (i) previously did not require a supplemental sample and the recomputed coefficient of variation does not exceed the survey limit, no additional samples are required;
   2. (ii) previously did not require a supplemental sample and the recomputed coefficient of variation exceeds the survey limit, additional samples are required;
   3. (iii) previously required a supplemental sample and the recomputed coefficient of variation exceeds the survey limit, new additional samples are required;
   4. (iv) previously required a supplemental sample and the recomputed coefficient of variation does not exceed the survey limit, no additional samples are required.
2. (2) Data changes occurring in an assessing unit in a county where a supplemental sample was required, subsequent to the completion of the supplemental sample, or in an assessing unit in a county where no supplemental sample was required, more than two months after the determination of the coefficient of variation and supplemental sample, will not affect the determinations of a coefficient of variation and supplemental sample.

(b) The following operations shall be performed in the determination of the supplemental sample:

1. (1) Compute the coefficient of variation for each municipality, borough of New York City, segment in a segment survey assessing unit, class in a special assessing unit or homestead assessing unit, school district designated in former 9 NYCRR section 186-6.1, as repealed in 1998 and set forth in section 1230 of the Real Property Tax Law, and class in a portion in a special assessing unit or homestead assessing unit:

   1. (i) During the computation of the market value ratio estimate pursuant to this Subpart, the contribution to the coefficient of variation of the estimate, or CV, is also estimated for each value interval.
   2. (ii) For the computation of the coefficient of variation for a class in a special assessing unit, each “U” interval is assumed to have a relative sampling variance proportional to its corresponding special assessing unit class relative variance. For the computation of the coefficient of variation for a class in a nonspecial assessing unit, each “U” interval is assumed to have a relative sampling variance proportional to its corresponding municipal relative variance.
   3. (iii) A coefficient of variation is not computed for the utility class. “S” intervals for the utility class are assumed to make no contribution to the sampling error since the intervals are not assigned their sample parcels by random selection methods.
   4. (iv) “T” intervals make no contribution to the sampling error.
   5. (v) All other “S” intervals contribute to the sampling error.
   6. (vi) The estimated coefficient of variation for each estimate is obtained by expressing the estimated standard error as a percentage of the ratio estimate.

2. (2) Determine the number of supplemental sample parcels necessary with respect to each municipality, borough of New York City, segment in a segment survey assessing unit, class in a special assessing unit or homestead assessing unit, school district designated in former 9 NYCRR section 186-6.1, as repealed in 1998 and set forth in section 1230 of the Real Property Tax Law, and class in a portion in a special assessing unit or homestead assessing unit.

   1. (i) If necessary, a supplemental sample is determined and the estimated coefficients of variation are tested in a multistep process. The order of the steps is as follows:

      1. (a) New York City:

         1. (1) municipal level;
         2. (2) borough level; and
         3. (3) for ordinary classes at the special assessing unit level.

      2. (b) Nassau County:

         1. (1) city and town level;
         2. (2) school district designated in former 9 NYCRR section 186-6.1, as repealed in 1998 and set forth in section 1230 of the Real Property Tax Law level; and

         3. (3) for ordinary classes at the following levels:

            1. (i) special assessing unit;
            2. (ii) city or town;
            3. (iii) village which has adopted the provisions of subdivision 3 of section 1402 of the Real Property Tax Law or town outside village; and
            4. (iv) school district.

      3. (c) Segment survey assessing units.

         1. (1) municipal level; and
         2. (2) segment level for any segment for which an equalization product is determined for the purposes of determining actual valuation pursuant to section 3602 of the Education Law or tax apportionment.

      4. (d) Homestead assessing units:

         1. (1) homestead assessing unit level;
         2. (2) for ordinary classes at the homestead assessing unit level;
         3. (3) school district portion designated in former 9 NYCRR section 186-6.1, as repealed in 1998 and set forth in section 1230 of the Real Property Tax Law; and
         4. (4) class level within a portion.
      5. (e) For all other municipalities, the municipal level.
   2. (ii) After the first step, the testing of the municipal estimated coefficient of variation, any hypothetical reduction to the CV attributed to any supplemental sample required in the first step or subsequent steps is assumed to have actually occurred prior to the test for the next step.
   3. (iii) At each step, the estimated coefficient of variation is compared to its corresponding CV limit shown herein.
   4. (iv) If the CV is greater than the appropriate CV limit, the sample size of the “S” interval contributing most to the CV is increased by one, the value interval contribution and CV are reduced hypothetically in accordance with sampling theory, and the adjusted CV is further tested against the CV limit. This process continues until the adjusted CV no longer exceeds the appropriate CV limit. If the initial CV estimate does not exceed the appropriate CV limit or a minimum number of supplemental samples is not assigned, no supplemental sample is assigned for the step. The minimum supplemental sample assigned is six for the following levels; municipal, borough, school district in a segment survey assessing unit, and school district designated in former 9 NYCRR section 186-6.1, as repealed in 1998 and set forth in section 1230 of the Real Property Tax Law.

   5. (v) The CV limits are:

      1. (a) For New York City:

         	CV limit
         Municipal-citywide	2%
         Borough	3%

      2. (b) For a class at the special assessing unit level the CV limit is 5 percent.

      3. (c) For a municipality, a segment in a segment survey assessing unit, and a school district designated in former 9 NYCRR section 186-6.1, as repealed in 1998 and set forth in section 1230 of the Real Property Tax Law:

         Estimated Market Value	CV limit
         0 to 64,499,999	6.0%
         64,500,000 to 128,999,999	6.0%
         129,000,000 to 257,999,999	6.0%
         258,000,000 to 386,999,999	6.0%
         387,000.000 to 515,999,999	6.0%
         516,000,000 to 644,999,999	6.0%
         645,000,000 to 773,999,999	5.8%
         774,000,000 to 902,999,999	5.6%
         903,000,000 to 1,031,999,999	5.4%
         1,032,000,000 to 1,160,999,999	5.2%
         Equal to or greater than 1,161,000,000	5.0%

      4. (d) For the following classes at a portion level the CV limit is 10%:

         Class

         Homestead

         Nonhomestead

         For an ordinary class in a special assessing unit

3. (3) Sample parcels and possible alternates are randomly selected for each interval where supplemental sample parcels are required. Sample parcels are appraised in accordance with this Part.
4. (4) Recompute the estimated market value ratio in accordance with the procedures set forth in section 8186-26.10 of this Subpart, with the inclusion of the supplemental sample parcels.