Why In News
The Election Commission of India has attracted criticism for reducing the Voter Verified Paper Audit Trail (VVPAT) based audit of Electronic Voting Machines (EVMs) to an exercise in tokenism and for its lack of transparency in the matter
The uniform sample size of “five Electronic Voting Machines (EVMs) per Assembly constituency” prescribed by it for all Assembly constituencies and States does not conform to the fundamental principles of statistical sampling and leads to high margins of error
Article 324: Superintendence, direction and control of elections to be vested in an Election Commission
The VVPAT-based audit of EVMs is a simple problem of statistical quality control.
It is very similar to the “lot acceptance sampling technique” that is widely used in industry and trade.
If the number of defectives found in a randomly drawn statistical sample is less than or equal to a specified acceptance number, the lot (or ‘population’) is accepted; otherwise, the lot is rejected
Here a ‘defective EVM’ is defined as one with a mismatch between the EVM count and the VVPAT’s manual count of voter slips due to EVM malfunction or EVM manipulation.
Unlike industry and trade where a few defectives in the sample may be tolerated, in the context of elections, the acceptance number will have to be ‘zero defective EVM’.
In other words, even if there is a single instance of mismatch between the EVM count and VVPAT manual count in the randomly drawn sample of EVMs, the ‘population’ of EVMs from which the sample was drawn should be ‘rejected’.
In this case, ‘rejection’ means non-acceptance of the EVM counts for that ‘population’ and doing manual counting of VVPAT slips for all the remaining EVMs of that ‘population’.
In such a scenario, the election result should be declared only on the basis of the VVPAT count.
Thus, VVPAT-based audit of EVMs involves three essential elements —
(a) a clear definition of the ‘population’ of EVMs from which the statistical sample would be drawn.
It could be all the EVMs deployed in an Assembly constituency, a Parliamentary constituency, a State as a whole, India as a whole, a region (or group of districts) within a State, or any other.
The population size (N) could vary widely depending on how we define the ‘population’;
(b) determination of a statistically correct and administratively viable sample size (n) of EVMs whose VVPAT slips will be hand counted;
(c) application of the ‘decision rule’, viz., in the event of a mismatch between the EVM count and the VVPAT count in the chosen sample of ‘n’ EVMs, the hand counting of VVPAT slips will have to be done for all the remaining (N-n) EVMs forming part of that ‘population’
When the population size (N) of EVMs is 100, the sample size (n) required is 99, that is it is nearly as big as the population size.
As N increases, n also increases but at a much slower rate and ‘hits a plateau’ beyond some point so that further increases in population size have no effect on the sample size
If we define the EVMs deployed in an Assembly constituency or Parliamentary constituency as the ‘population’, then in view of the smaller population sizes (N), the sample sizes (n) required are rather big.
Hence, both these choices for ‘population’ are administratively unviable
If we define the EVMs deployed in a State as a whole or India as a whole as the ‘population’, then in view of the bigger population sizes (N), the sample sizes (n) required are very small
But the workload involved in hand counting the VVPAT slips for all the remaining (N-n) EVMs of the population, in the event of a mismatch, is very large and administratively unviable for India as a whole and for all States except the smaller States
Way Forward
The Supreme Court must compel the ECI to make public how it has defined the population, how it has arrived at its sample size, and most importantly, its decision rule in the event of a mismatch.
Only then, the Supreme Court’s order of 2013 on VVPAT would be implemented faithfully in letter and spirit.
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