For instance, for KMEX's telenovela "Volver a Empezar," NSI lists the program as being viewed in 244,000 households, while NHSI lists the show as being viewed in 454,000 households.
KMEX would like to reconcile the numbers by merging the two Nielsen systems.
"Nielsen has been producing two different sets of numbers which are out of statistical tolerance," said Maureen Schultz, KMEX's director of research and marketing.
"We're looking at 28% to 86% differences. So we went to Nielsen and said, `Explain why the numbers are different.' NSI has not kept pace with its methodology and sample frame. If it's measuring one-quarter of the market, the entire market cannot be correct. General market station ratings are being overstated by the wrong methodology."
Nielsen uses set-tuning meters and diaries for its NSI sample and people meters for its NHSI sample.
According to Ms. Schultz, some English-language stations in the market feel the NHSI methodology is better than the NSI system.
In a letter sent to NSI subscribers responding to KMEX's claims, Nielsen Exec VP Robert Taragan wrote that: "Nielsen believes that the NSI service is the benchmark for measurement of the Los Angeles television market. The NSI service, which has been refined over the years in close consultation with our customers, is the best possible audience measurement for this complex and diverse market."
Mr. Taragan cited the differing methodologies, but added, "At some point, in consultation with all of our customers, we may wish to consider some crossover involving the two samples."
Mr. Tiegel is a correspondent for Electronic Media.