All four polling experts interviewed yesterday raised concerns about potential bias in the response pool.

Francis J. Connolly ’79, a senior analyst at the Boston-based public-opinion research firm Kiley & Company, said the response may have disproportionately represented one group in the debate over Summers’ tenure.

“There’s always the potential that Faculty members on one side of the issue or the other might have more of an incentive to respond and that the results would be biased accordingly,” said Connolly, a former Crimson president.

The poll was also examined by Nancy Belden, president of the American Association for Public Opinion Research, and Michael McDonald, a polling analyst at the non-partisan Brookings Institution.

Though respondents were assured anonymity, some faculty critics of Summers said they were reluctant to respond for fear of retribution from the central administration. One professor who asked not to be named said the chair of his department instructed faculty to respond to the poll by phone rather than e-mail to avoid creating a written record of their dissent.

Some faculty who favored Summers said they did not want to respond because they were concerned powerful colleagues who have criticized the president might penalize them.

—Staff writer Zachary M. Seward can be reached at seward@fas.harvard.edu.

POLL RESULTS

Do you approve of Summers’ leadership of the University?

Approve: 108 (40%)

Disapprove: 140 (52%)

Don’t Know: 22 (8%)

Total: 270

What effect do you think Summers has had on Harvard’s image?