A Statistical Quality Management Framework for

Contents
Page
1 of 5
Print
A Statistical Quality Management Framework for
Sample Surveys in an Official Statistical Agency
Sessions
STCPMs
Marlize Pistorius; Luthando Mayekiso
Statistics South Africa. De Bruyn Park Building, 170 Andries Street, Pretoria 0002, South Africa.
E-mail: MarlizeP@statssa.gov.za; LuthandoMa@statssa.gov.za
Statistics can be seen to be produced by a Statistical value chain (SVC). The most general or complete form
of the SVC can be seen as that which emanated from the Joint UNECE/Eurostat/OECD Work session on
Statistical metadata [1], which is called the Generic Statistical Business Process Model (GSBPM). The
GSBPM is composed of ten high level business activities, namely, specify needs, design, build, collect,
process, analyse, disseminate, archive, evaluate, and a quality management or metadata management. Each
of these high level activities can be further decomposed into lower level activities, usually composed of three
to nine sequential sub-activities. The sub-activities and any further decomposition of these activities have an
impact in the final statistical quality of the estimate that emanates from the process.
T
Contents
Page
2 of 5
Print
The statistical quality can be measured using a statistical quality assessment framework. In the South African
setting such a framework is called the South African Statistical Quality Assessment Framework (SASQAF),
and is composed of nine dimensions, namely, pre-requisites of quality, relevance, accuracy, timeliness,
accessibility, interpretability, coherence (and comparability), methodological soundness and integrity.
Another example is the Eurostat quality indicators [2], which is more suitable for the Euro region setting, but
Sessions
STCPMs
can be adapted to other settings. The Eurostat quality indicators have the advantage of being more
quantitative in nature, and are thus more amenable to mathematical optimization.
An optimal method to depicting and analyzing business processes is the Business Process Modeling Notation
(BPMN) 1 and the IDEF0 2 diagrams. In Business Process Modeling Notation (BPMN) one has activities,
flow arrows, events and gateways. The activity describes a work function performed by the process. The
activity can be a sub-process which is a compound process that can be further collapsed into component
activities. A flow is an icon used to show the order in which activities in the process take place, and an event
is an occurrence in the environment of the process. A gateway is used to control the joining or separation of
flows in the process. The IDEF0 diagram is comprised of a hierarchical set of diagrams, namely, a context
diagram (A-0), a top-level diagram (A0), a decomposition diagram, a node diagram, and a for exposition
T
1
Business Process management initiative, www.bpmi.org
2
Institute of Electrical and Electronic Engineers (IEEE) Std 1320.1-1998 (R2004)
Contents
Page
3 of 5
Print
only (FEO) diagram. The modeling notations allow one to depict the business process using software such
a Telelogic System Architect, iGrafx FlowCharter, WorkFlow Analyzer, AI0win, iGrafx IDEF0, ARIS, and
Visio.
The methods of Business Processes Redesign build on Business Process mapping concepts in order to
Sessions
STCPMs
improve or increase the value added of the business process as defined by desired outcome. In the context of
a Statistical Quality Management Framework within an Official Statistical Organization, one can make the
simplifying assumption that better outcomes or better quality decisions will emanate from decisions made
from better quality statistics. This then allows one to use the quality management framework to define real
value adding activities, business-value-added, and non-value adding activities or alternatively loss functions,
which are expenditures on the value chain that do not improve the statistical quality.
In Business Process Redesign one wants to redesign in an innovative manner key business processes to
achieve breakthrough improvements in business performance. Generally this involves improving activities,
restructuring and reconfiguring process flows, changing information flows around processes, changing
knowledge management around processes and configuring roles around processes.
T
In a Bayesian decision theory framework one can use the Statistical Quality Assessment framework to define
Contents
Page
4 of 5
Print
statistical value. This can be used to define a loss function or a utility function. In this framework we let
θ={θ1, θ2} be the state of nature about the quality improvement of a particular action. Then one can, using
techniques outlined in [3], let A={a1, a2} represent two expenditure actions of equal size from fixed budget of
resources. Assuming no data is available one can let π(θ) represent the probability distribution of θ and
define an Expected Bayesian loss of each action ai, i=1 or 2, as ρ(π, ai)=Eπ L(θ, ai)=∫Θ L(θ, ai)f(x| θ)dθ. Then
Sessions
STCPMs
using the Conditional Bayes Principle, one can choose the action ai, i=1 or 2, that minimizes ρ(π*, ai), where
π(θ) is the prior distribution of θ, and π*(θ) is the posterior distribution of θ.
The South African Quarterly Labour Force Survey was re-engineered according to actions outlined in [4] the
standard error of the overall official unemployment estimate in September 2008 according to the Quarterly
Labour Force Survey standard error was 74 196 while in September 2007 it was 115 306 (not taking into
account other changes).
REFERENCES )
[1]
T
Joint UNECE/Eurostat/OECD Work Session on Statistical Metadata (METIS) (2008), Generic
Statistical Business Process Model.
Contents
Page
5 of 5
Sessions
STCPMs
Print
T
[2]
Quality in Statistics (2005), Seventh Meeting, Eurostat, Doc.ESTAT/02/quality/2005/9/quality
indicators.
[3]
J. Berger (1985), Statistical decision Theory and Bayesian Analysis, Springer-Verlag.
[4]
Statistics South Africa (2008), Report on the response by Statistics South Africa to recommendations of
the International Monetary Fund on improvements to the Labour Force Survey.