CMHC does not publish a statistic if its reliability is too low or if publication of a statistic would violate confidentiality rules. The ability to publish an estimate is generally determined by its statistical reliability. As indicated earlier, CMHC currently uses the coefficient of variation (CV).

A letter code representing the statistical reliability (i.e., the coefficient of variation (CV)) for each estimate is provided to indicate the data reliability. CV of an estimate is defined as the ratio of the standard error of the estimate to the estimate itself and the CV is generally expressed a percentage. For example, let the average rent for one bedroom apartments in a given CMA be  and its standard error be . Then the Coefficient of Variation is given by

RELIABILITY CODES FOR PROPORTIONS

CMHC uses CV, sampling fraction and universe size to determine the ability to publish proportions. The following letter codes are used to indicate the level of reliability of proporations:

A — Excellent
B — Very good
C — Good
D — Fair (Use with Caution)
** — Poor — Suppressed

The following two tables indicate the level of reliability of Proportions:

If the proportion is zero (0) and the sampling fraction less than 100% then the following levels are assigned:

Sampling Fraction (%) range
Structures in Universe(0,20]*(20,40](40,60](60,80](80,100)
3 – 10PoorPoorPoorPoorPoor
11 – 20PoorFairFairFairGood
21 – 40PoorFairFairGoodVery Good
41 – 80PoorFairGoodGoodVery Good
81+PoorGoodGoodVery GoodVery Good

Otherwise, the following table is used to determine the reliability level of proportions:

Coefficient of Variation (CV) %
Percentage0(0, 5](5, 10](10, 16.5](16.5, 33.3](33.3, 50]50+
(0, 0.75)ExcellentExcellentExcellentExcellentExcellentV. GoodV. Good
(0.75, 1.5)ExcellentExcellentExcellentExcellentExcellentFairPoor
(1.5, 3)ExcellentExcellentExcellentV. GoodGoodPoorPoor
(3, 6)ExcellentExcellentV. GoodGoodFairPoorPoor
(6, 10)ExcellentExcellentV. GoodGoodPoorPoorPoor
(10, 15)ExcellentExcellentGoodFairPoorPoorPoor
(15, 30)ExcellentExcellentFairPoorPoorPoorPoor
(30, 100)ExcellentExcellentPoorPoorPoorPoorPoor

*(0, 20] means sampling fraction is greater than 0% but less than or equal to 20%; others are similar

RELIABILITY CODES FOR AVERAGES AND TOTALS

CMHC uses the CV to determine the reliability level of the estimates of average rents and a CV cut-off of 10% for publication of totals and averages. It is felt that this level of reliability best balances the need for high quality data and not publishing unreliable data.

CMHC assigns a level of reliability as follows (CV’s are given in percentages):

A — If the CV is greater than 0 and less than or equal to 2.5 then the level of reliability is Excellent.
B — If the CV is greater than 2.5 and less than or equal to 5 then the level of reliability is Very Good.
C — If the CV is greater than 5 and less than or equal to 7.5 then the level of reliability is Good.
D — If the CV is greater than 7.5 and less than or equal to 10 then the level of reliability is Fair.
** — If the CV is greater than 10 then the level of reliability is Poor. (Do Not Publish)

 

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Date Published: March 31, 2018