Methods of measurements of errors have been developed for
census statistics; however can equally be used in vital statistics
registration.
Response error is a broad term which includes both errors of
coverage and error of content. The sampling theory assumed the census or survey
or VSR records collected at time period are regarded as one of the series of trials,
collection of responses which would vary from trial to trial. This hypothesis
further assumed that the trials have been conducted under the same conditions
and that they are independent of each other.
Count in Census(Ideal/ Standard) / Survey


C
O
N
T
E
N
E
V
A
L
U
T
I
O
Survey

Number of persons in count

Number of Person not in count

Total


Number of person in class

a

b

a+b


Number of person not in class

C

d

c+d


Total

a+c

b+d

·
Then (a+c) represent count in a census/ sample
survey/ VSR in relation to birth, death etc.
·
(a+b) is the corresponding count in CES
·
“a”
is the number appearing in both
·
And on the other hand c would occur in actual
·
And “d” is the number without count
characteristic and vital counts.
i.
Net difference rate (NDR).
ii.
Gross difference rate (GDR).
iii.
The index of net shift relative to ideal or
standard count.
iv.
Index of stability.
v.
Index of inconsistency.
1) NET DIFFERENCE RATE (NDR):
The net difference rate is defined as
NDR=(cb)/n *100
It provides an estimate of the extent of
the biased in the actually observed count (a+c). A positive value of the rate
indicates an over statement, while a negative value indicates an under count in
census survey or VSR. In case of no error the value would be zero.
2) GROSS DIFFERENCE RATE:
GDR assumed in a hypothetical situation of repeated response from the
same person in a large series of census/survey or VSR conducted under same
conditions that a record is made of the response deviation for some person on
each trial from the average of all responses. Hence the gross difference rate
is defined as
g= b+c/n*100
And the simple response variance is
approximated as;
SRV =1/2g
3) The index of net shift relative to
ideal standard count:
It is defined as the ratio of the differences in the count with the
total in ideal count. Its positive indicates over estimate and negative
indicates an under count.
s =cb/a+b*100
4) Index of stability:
The index of stability is a ratio which shows a number with specified
characteristics which included in both, the census/ survey/ VSR with relation
to those characteristics in the ideal or standard count. In terms of notation
adopted this index is defined as:
Index of stability= a/a+b*100
This indicates the stability of response,
the census survey or VSR relative to the ideal or standard count.
5) Index of consistency:
The index of consistency which is also the measure of the stability of
response is defined as;
I = g/2p(1p)*100
Where p (1p) is estimated by the average
of sampling variance of the proportion having same characteristics such as
specified occupation in census survey or VSR in the ideal situation or standard
count.
Generally I vary between 0 ≤ I ≤100
However
values of I greater than 100 may arise occasionally when small sample are
involved or if the assumption of estimation is completely not valid. A large
value of I indicates a high degree of response error, an index of the stability
of response “r” is more readily understood than I.
However
it should be recognized that I and r are complementary in the sense that a
large number of response error by a large value of I and by a small value of
“r”.
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