Many people appear to be confused about what it means to be members in their churches -- that is, if they know their church offers membership at all.

A new study from Grey Matter Research indicates that 33 percent of worshipers surveyed believe their church does not offer any sort of membership, while 19 percent said they were not sure. This means that less than half of respondents know about membership offerings in their church.

Yet, all 10 of the largest denominations in the U.S. -- including the Roman Catholic Church, Southern Baptist Convention, United Methodist Church, and Church of Jesus Christ of Latter-day Saints -- offer some form of official church membership. Among constituents of these denominations, however, only 44 percent say their church offers official membership. Nearly 40 percent of attendees believe these churches do not offer membership, while 17 percent are unsure.

Protestants are more likely than Catholics to be aware of church membership options, and evangelicals are most likely of all to know about membership at their church. Compared to 44 percent of all respondents, 72 percent of evangelicals said their church offers membership.

Many denominations continue to measure their size according to official membership, said Ron Sellers, president of Grey Matter Research.

“Under half of all Americans who attend religious services believe they can officially join their church or place of worship,” Sellers said. “The question has to be asked –- how relevant are membership statistics as a measure of denominational size or reach in today’s world?”

CT previously covered the membership-related decrease in church giving during the recession.