The survey has its limitations. It is unclear exactly when the retired senior officers left the department, making it impossible to say whether any alleged manipulations came early on or had developed over years and across more than one mayoral administration. The CompStat approach has been widely replicated across the country and has been credited with improving police work in many cities.

Image Rudolph W. Giuliani in 1995 with William J. Bratton, left, who instituted CompStat. A police spokesman criticized a survey of hundreds of retired police officials. Credit... James Estrin for The New York Times

Also, the questionnaires did not set out to measure the frequency of any manipulation. None of the respondents were asked to identify specific acts of misconduct, and none admitted to having done it themselves. In addition, it was unclear whether the officials who said they were aware of unethical conduct had firsthand knowledge.

But the survey asked provocative questions and clearly elicited disturbing answers. The retired members of the force were asked whether they were aware of changes to crime reports. Of the 160 who indicated that they were, more than three-quarters said the changes were unethical.

Paul J. Browne, the Police Department’s chief spokesman, who was provided a copy of the survey’s summary Thursday, said that two other significant, independent and more comprehensive studies had been done in recent years analyzing the integrity of the city’s crime statistics — one in 2006 by a New York University professor and another by the state comptroller’s office — and that he had found them to be reliable and sound.

The report by the N.Y.U. professor, Dennis C. Smith, contained this assessment: “We conclude, as did the state comptroller five years ago, that the city and department officials, and the public can be reasonably assured that the N.Y.P.D. data are accurate, complete and reliable.”

The researchers in the new survey emphasized that the responses — the questionnaires were mailed in September 2008 and returned in early 2009 — showed that most of the senior officers believed that CompStat had been a valuable management innovation. And even few department critics would seriously dispute that the city is much safer than it was in the early 1990s, with murders cut by nearly 80 percent and with neighborhoods, from the notoriously violent to the largely affluent, transformed.