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1
A Study of Sources for the Error Structure in Estimates
of Census Coverage Error Components
Mary H. Mulry
U.S. Census Bureau
2009 International Total Survey Error Workshop
June 16, 2008
2
Census Coverage Error Definitions
• Net census coverage error = omissions – erroneous enumerations
• Components of coverage error• Erroneous enumerations• Omissions
• Estimated net error in Census 2000 was small, but evidence indicated component errors were larger
3
Net census coverage error• DSE used to estimate net coverage error• Case-by-case matching of enumeration(E) &
independent population(P) samples • Processing employs balancing of errors that
improves net error estimates
• Net error estimate is unbiased if no model error: net error = DSE – census
• However, balancing of errors causes upward bias in weighted nonmatches and weighted erroneous enumerations
• Not suitable for component errors
4
Components of coverage errors omissions & erroneous enumerations
• Component error estimation needs processing without balancing of errors needed for net error• Collect more data from respondents• More processing of DSE data • Different estimators
• Estimators: EEs = weighted erroneous enumerations Omissions = net error + EEs
5
Error structure in component errors
• Recent studies (Mulry 2008, Spencer 2008)
• Error structure in estimate of erroneous enumerations yields understanding of error structure in estimate of omissions
• Some offsetting of errors in estimates of omissions• Errors present in estimate of EEs for net error
offset in estimate of EEs for components
6
Definition of Components of Census Coverage Error
• Erroneous enumerations• Duplicate enumerations• People born after Census Day• People who died before Census Day• Enumerations for people not residents of a HU in the U.S.
• Omissions• People who should have been enumerated in the Census
but were not
7
Definition of Correct Location for Enumeration
• For net error• Persons must be enumerated in a
HU within the search area of their ‘usual residence’
• For component errors• Persons must be enumerated in a
HU once anywhere in the U.S.
8
SufficientInformation for
Net Error Processing
InsufficientInformation for
Net Error Processing
Data-DefinedEnumerations
Various Levels ofM issing Data
(census imputes)
Non-Data-DefinedEnumerations
Census
Varying amounts of data reported for Census enumerations
E1 E0
9
Data-defined EnumerationsE1 has sufficient info for net error
CE1 = correct enumerations
EE1 = erroneous enumerations
WL1 = enumerations in wrong location, but only enumeration for person
E0 has insufficient info for net error
CE0 = correct enumerations
EE0 = erroneous enumerations
WL0 = enumerations in wrong location, but only enumeration for person
10
Estimates of Erroneous Enumerations
EE EE WL Enet 1 1 0
EE EE EEcom ponen t 1 0
11
Notation for errors in status in enumeration sample
True statuscoded status
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True status vs coded status for enumeration sample
coded status correct erroneous wrong location
correct CE CE EE CE WL CE
erroneous CE EE EE EE WL EE
wrong location CE WL EE WL WL WL
True status
Subscript is coded status
True values are sums of columnsEstimates are sums of rows
13
Net error terms are important for component error estimates
e CE W LWL CE W L CE
e EE W LWL EE W L EE
e CE EECE EE EE CE
14
Types of errors in data
• Identification of duplicate enumerations
• Membership in housing unit population
• Usual residence
• Geocoding housing unit containing the enumeration
15
How Errors Occur
Failure to detect
False detection
Types of errors•Duplication•Population member•Usual residence•Geocoding
16
Correct Enum coded Erroneous
•False duplicate
•Undetected HU pop member
•Undetected usual residence•Has duplicate that is misclassified as usual residence
Erroneous Enum coded Correct
•Undetected duplicate
•Falsely HU pop member
•False usual residence•Has duplicate that is usual residence
17
Correct Enum coded Wrong Location
•Undetected usual residence•Another HU misclassified as usual residence & not enumerated there
•False geocoding error & only enumeration
Wrong Location coded Correct Enum
•False usual residence•Another HU is usual residence & not enumerated there
•Undetected geocoding error & only enumeration
18
Erroneous Enum coded Wrong Location
•Undetected duplicate •Misclassified as only residence, but also enumerated at usual residence
•Falsely HU pop member •Misclassified as in HU pop at wrong location
Wrong Location coded Erroneous Enum•False duplicate
•Usual residence outside search area & not enumerated there
•Undetected HU pop member at wrong location
19
Sources of errors
• Processing errors• 2 studies evaluate 2010 CCM
• Data collection errors• 4 studies evaluate for 2010 CCM
20
Info on processing error
• Matching Error Study• All types of errors
• Administrative Records Study• Types of error: Duplication, HU pop
21
Info on data collection error
• Respondent debriefings• Types of error: usual residence, HU pop
• Study of Missed Housing Units• Type of error: geocoding
22
Info on data collection error
• Recall bias study• Type of error: usual residence
• Comparison of census operations with CCM results• Type of error: geocoding
23
Summary of error sources
• Synthesis of info from CCM evaluations • Designing simulation study to aid
analysis of error structure
• Develop better understanding of error structure