PHILADELPHIA — The University of Pennsylvania is at the forefront of a movement to experiment with free open online courses, but the undertaking, as its own researchers are finding out, has yielded mixed results.

While Massive Open Online Courses (MOOCs) have attracted millions of viewers and been heralded as a potential way to address skyrocketing tuition, very few of their viewers — 4 percent, on average — actually complete the courses, according to the latest study by researchers in Penn’s Graduate School of Education.

Many who register drop off after the first week or two, the researchers found in a study they will present Thursday at a MOOC conference at the University of Texas-Arlington. About half who registered viewed at least one lecture.

The results come on the heels of another Penn study, released last month, that showed a vast majority of students enrolled in MOOCs already hold college degrees and are taking the courses primarily to advance in their jobs, which called into question the notion that the courses were providing greater access to the world’s underprivileged.

“The technology offers some promise of a new approach to addressing both” costs and access, said Laura Perna, a lead researcher on the new study. “We just don’t know to what extent this is going to be more than a promise.”

The researchers looked at 1 million users who registered for the 16 free courses offered from June 2012 to June 2013, among them “Calculus: Single Variable,” “Greek and Roman Mythology” and “Fundamentals of Pharmacology.” The classes were taught by Penn professors and offered in partnership with Coursera, a California-based online education company and a pioneer in MOOCs.

The study, conducted by the newly created Alliance for Higher Education and Democracy at Penn, delved into when users enter and leave courses and when and how they participate. The courses varied in use of quizzes and homework and instruction time. Completion rates were slightly higher in courses with smaller workloads.

Most courses focused on personal enrichment or occupational skills, such as “Cardiac Arrest, Resuscitation Science and Hypothermia.”

Perna said she was a bit surprised by the results.

“Four percent is low. I didn’t expect it to be quite this low,” she said.

But Ed Rock, who heads Penn’s MOOC initiative, called the findings “entirely unsurprising and not at all troubling. Four or five percent of 1.6 million (current users) is still 80,000 people, and 80,000 people is a huge number to educate.”

Rock, senior adviser to the president and provost and director of open course initiatives, also said those who do not complete have gotten something from the experience.

The majority of MOOC users are doing it for leisure learning or job development, so it’s not surprising that few finish, said Cathy Sandeen, vice president for education attainment and innovation at the American Council on Education.

“There is a place for MOOCs in terms of degree attainment, but it’s probably a smaller component overall than we might have originally thought,” she said.

Rock acknowledged that educators have a way to go in learning how best to fit MOOCs into the educational mission. Penn has partnered with 10 high schools locally and nationally whose teachers are using Penn’s calculus course to supplement classroom learning.

“Our hope is our material will be of value. We won’t know that unless [high school teachers] try it out and tell us,” he said. “We believe these materials have the potential to revolutionize education, but they’re only going to work in a partnership.”

Perna, whose team includes researchers Alan Ruby, Robert Boruch, Nicole Wang, Janie Scull, Chad Evans and Seher Ahmad, agreed that MOOCs could benefit society. She cited the case of a neighbor who is taking a management MOOC with co-workers who meet each week to discuss what they’ve learned.

“I think there is something there,” she said, “but we need to understand better what that contribution is. Penn is clearly committed to exploring these issues.”