= 2007 ACS Standard Quality Public Housing Adjusted Median Rent / 2006 ACS Standard Quality Public Housing Adjusted Median Rent
= $643
/
$632
= 1.0174
New for Final FY 2010 FMRs, HUD tests to see if the change in ACS survey results from 2006 to 2007 is statistically significant.
This is done by computing a "Z-Score". If the Z-Score value is greater than 1.645 the 2 survey results are considered to statistically different from each other.
If the Z-Score is less than 1.645 then the change as measured by the two surveys is considered to be statistically insignificant and the change factor is set to 1.0
The Z-Score is calculated as:
| Z | = | ABS(EST07 - EST06)
 (SE072 + SE062) |
|
Where EST06 is the 2006 ACS Survey Estimate, EST07 is the 2007 ACS Survey Estimate, SE06 is the standard error of the 2006 ACS Survey Estimate and SE07 is the
standard error of the 2007 ACS Survey Estimate.
| Z | = | ABS(643 - 632)
(4.8632 + 4.8632) |
|
| Z | = | 11
(23.651 + 23.651) |
|
| Z | = | 11
47.302 |
|
| Z | = | 11
6.878 |
|
Z = 1.599
As can be seen from the calculation above the z-score is not greater than 1.645. Therefore the 2006 to
2007 update factor is 1.0.