A larger group of students than originally tallied may have received erroneous scores after taking the October 2005 SAT Reasoning Test.

Last week, the College Board discovered 1,600 tests that had not been rescored to check for errors. Some of these tests may soon be added to the approximately 4,000 — 0.8 percent of October tests — that had their scores increased after the company discovered grading errors made by its machine scanners.

Yale and other universities were notified of initial score changes two weeks ago and may receive more changes this week. College Board representatives said they expect few students to see their admissions decisions affected by score changes, but critics said the mistake could have serious consequences for college applicants. Dean of Undergraduate Admissions Jeff Brenzel said no admissions decisions have been reversed due to the 75 score changes Yale received, as the SAT is only one of many factors considered in applications.

“The great majority of the scores changed by only 10 to 30 points total out of 2,400,” Brenzel said in an e-mail. “All of the erroneous scores have been updated in our database, and admissions staff have reviewed applications of the students affected.”

Though the error’s impact on Yale applicants is not significant, Brenzel said, University officials are concerned about the College Board’s current scoring procedures. Along with other universities, Yale officials will be reviewing what mechanisms the College Board puts in place to avoid a repeat occurrence, he said.

College Board officials originally said they had corrected the problem by March 6 — having changed scores and refunded testing fees for students whose corrected scores were higher than first reported — but announced last Tuesday that about 1,600 additional exams, which had been put on administrative hold and separated from the other test papers, had not yet been vetted for scoring errors. They said college officials will be notified this week if any changes on these papers are made.

But Robert Schaeffer, public education director for the advocacy group FairTest, said the error could weaken the role of standardized testing in the college admissions process.

O’Reilly said the College Board first became aware of a possible grading problem in late January, after discovering scoring errors on the tests of two students who asked that their exams be regraded by hand. Following an investigation, he said the company determined that only the October exams had been affected. All the tests were rescored, O’Reilly said, and colleges were notified of changes.

The errors were likely caused by excessive moisture in some papers, causing them to expand and move the bubbles slightly, O’Reilly said. Light pencil marks may not have been picked up by the scoring machines, which are run by Pearson Educational Measurement, he said.

O’Reilly said the test scanners have been equipped with paper measuring software to detect similar problems in the future, but College Board officials have not determined why moisture affected the October exams in particular, or at what point in the testing and grading process the damage occurred. Tests from 20 countries and all 50 states were affected, he said. About 83 percent of the changes were by 40 points or less, and fewer than 150 students, as counted so far, had an increase of 100 points or more.

Several high school students said they are alarmed by the scoring problems.

“Well, I’m really glad that didn’t happen to me,” said Jessica Cooper, a senior at Miramonte High School in California. “I would be really stressed out … especially at this time, when colleges are making their decisions.”

Madeleine Myers, a senior at the Bronx High School of Science in New York who was also deferred after applying early to Yale, said she is disappointed in the College Board.

“They are such a large part of the college process, and to find out that they can’t even grade their tests properly is upsetting,” Myers said. “If I had [a scoring error and] applied early and had been deferred and moved into the regular pool, which is much more competitive, I would have been very upset.”

The College Board announced earlier this month that the grading error also affected about 600 students who performed worse on the October exam than their original scores indicated, but the company will not notify colleges of these errors so as to not penalize students who might have otherwise retaken the SAT.