IAS Gyan

Daily News Analysis


2nd May, 2024 Polity


Copyright infringement not intended

Picture Courtesy: https://economictimes.indiatimes.com/news/politics-and-nation/eight-cases-of-vvpat-evm-mismatch-in-lok-sabha-polls/articleshow/70323347.cms?from=mdr

Context: Activists raised a demand for a statistically sound VVPAT-based system of EVM audit that can detect instances of mismatch with 99% or 99.9% certainty.


  • The challenges and limitations of verifying electronic voting machines (EVMs) using Voter Verifiable Paper Audit Trail (VVPAT) systems stress the use of statistical principles in developing effective audit methods to assure the accuracy and integrity of election systems.

Electronic Voting Machines (EVMs)

●An EVM is an electronic device used for recording votes, consisting of a Control Unit and a Balloting Unit. Voters cast their votes by pressing buttons on the Balloting Unit.

●EVMs were first used in the Parur Assembly Constituency of Kerala in 1982.

●EVMs operate on batteries and do not require electricity.

●EVMs can record up to 2,000 votes. The number of candidates accommodated varies with different EVM models (up to 64 candidates with M2 EVMs and up to 384 with M3 EVMs).

●If an EVM malfunctions during polling, it is replaced without affecting the votes already recorded.

●EVMs are designed by the Technical Experts Committee of the Election Commission in collaboration with Bharat Electronics Ltd. (BEL) and Electronics Corporation of India Ltd. (ECIL).

Voter Verifiable Paper Audit Trail (VVPAT)

●VVPAT is a system attached to EVMs that provides a paper trail for voters to verify that their votes are cast as intended.

●VVPAT does not run on electricity and uses a battery power pack.

●Voters can verify their votes through a printed slip containing the serial number, name, and symbol of the chosen candidate; it remains visible through a transparent window before falling into a sealed drop box.

●VVPATs were first used in a bye-election in the Assembly Constituency of Nagaland in 2013.

Challenges with EVM Audit

Sample size and statistical accuracy

  • The present mandatory sample size of “5 EVMs per Assembly Constituency” for VVPAT-based audits is statistically inadequate.
  • According to statistical sampling theory, the current sample size makes the probability of missing to discover a malfunctioning EVM unacceptably high.
  • A bigger sample size is required to provide a higher level of confidence (e.g., 99% or 99.9%) in identifying suspected EVM failure or manipulation.

Definition of Population and Audit Protocols

  • One important concern is the ambiguity surrounding the concept of the 'population' of EVMs to which the required sample size applies.
  • The 'population' should be clearly specified to identify the proper audit scope and further steps in the event of detected mismatches.
  • If any malfunctioning EVMs are discovered in the sampling audit, all EVMs within the identified 'population' should be manually counted using VVPAT slips to assure the accuracy and integrity of the voting process.

To restore public trust in the electoral process, courts and election officials should seek expert advice and use scientifically sound EVM auditing procedures.

Way Forward

Statistically Sound Auditing System

  • There is a need to create a statistically accurate VVPAT-based audit system that can detect errors in EVM counts with high accuracy (e.g., 99% or 99.9%).
  • This involves modifying the sample size requirements using statistical sampling concepts to facilitate the effective detection of any EVM concerns.

Clear Definition and Protocol

  • Clear definitions of the 'population' of EVMs are required, as well as clear audit protocols detailing what actions should be performed if errors are identified.
  • If any malfunctioning EVMs are discovered throughout the audit process, manual counting of VVPAT slips should be expanded to include the full designated 'population'.

Implementation and transparency

  • Implementing the proposed modifications should prioritize transparency and statistical best practices.
  • The electoral authorities should work with statisticians and auditors to build and implement a strong VVPAT-based audit system that ensures the electoral process's integrity.

Acceptance Sampling

● Acceptance sampling is a statistical measure used in quality control to determine the quality of a batch of products by testing a representative sample.

●It involves selecting a sample from a batch of products, testing them for defects, and deciding whether to accept or reject the entire batch based on the results of the sample.

It is used when testing every product in a batch is impractical due to time or cost constraints, or when testing would render the product unusable (destructive testing).

It is a quick method to make immediate decisions about batch quality, while comprehensive quality control involves systemic measures to ensure consistent quality throughout production.

It doesn't guarantee 100% quality assurance, and there's always a risk of accepting defective products or rejecting good ones based on the sample results.


  • Statistical concepts play an important role in maintaining the accuracy and integrity of EVM audits conducted using VVPAT. It advocates for a more comprehensive approach to sample size determination, clear definitions of audit populations, and transparent methods for dealing with discovered disparities. By implementing these modifications, electoral authorities can build public trust and confidence in the election process by displaying a commitment to statistical integrity and openness in EVM audits.

Must-Read Articles:


Electronic Voting Machine (EVM)


The Hindu


Q. In light of the recent controversy regarding the use of Electronic Voting Machines (EVM), what are the challenges before the Election Commission of India to ensure the trustworthiness of elections in India?  (UPSC 2018)