A study by Ohio State University claims Facebook users spend less time studying and get lower grades than classmates who don’t use the site. But there are some serious flaws in the study’s logic.

A survey of 219 students found that 85% of undergraduates use Facebook. Those who do have grade-point averages between 3.0 and 3.5, while those who don’t have averages between 3.5 and 4.0. Facebook users averaged one to five hours a week of studying, while non-users averaged 11 to 15 hours. Students disagree with the conclusions, with 79% of Facebook users claiming the site didn’t affect academic performance.

The problem with studies such as this is that they assume a link between two facts: as the saying goes, correlation does not equal cessation. It’s entirely possible that the type of students who use Facebook are the type of people who are less likely to study in the first place and that Facebook is simply how they choose to fill the time that comes from not studying.

To be fair to the study author, Aryn Karpinski, she does state that “It cannot be stated (that) Facebook use causes a student to study less. I’m just saying that they’re related somehow, and we need to look into it further.”

The figures themselves are also pretty vague. The study report doesn’t give specific figures about the grades and simple says the students’ results “generally” fitted into the stated ranges. That makes it tough to tell exactly how significant the differences between Facebook users and non-users was.

It’s also worth nothing that 85% of the 102 undergraduate students were regular Facebook users. That means that the comparison for undergraduate students is the behavior of 87 people against that of just 15. That leaves a pretty significant margin of error.

The study didn’t break down the results for either study time or grades between undergraduates and graduates. That provides further room for misleading results as of the non-Facebook-users, barely a fifth were undergraduates. It’s not exactly a fair comparison to stack up undergraduate grades against those of graduates, or to compare the commitments to putting in the hours of studying.

About the only conclusion you can be reasonably confident about from this study is that people who study for longer generally get better grades. But that’s hardly news worth posting a status update about.