Congrats on your 1,500 LinkedIn connections. But did they help you snag a job?

Weak online connections on job sites and social networking sites are no match for “strong connections” — i.e., close friends and family members with whom you communicate at least once a month — when it comes to landing a gig, according to a new study from the Institute for Operations Research and the Management Sciences.

The survey of 424 college-grad LinkedIn users, published this week in the INFORMS journal Management Science, asked about various job-search avenues: job sites like Monster.com, social-networking sites like LinkedIn, print media, close friends and family offline, and career centers and recruiters. It also took stock of how many leads, interviews and offers those channels spawned, and measured the number and strength of the job hunters’ connections.

Job sites produced the most leads, and weak LinkedIn connections yielded slightly more leads than strong connections — but interviews and offers were most likely to come from strong ties, the study found. In fact, a 10% increase in strong ties — roughly a one-tie bump — increased job offers by 0.7% on average. Increasing weak ties by 10% — the equivalent of about 10 ties — seemed to diminish the number of offers by 1.3%.

“We found that strong ties have a significant and positive effect on job interviews,” study co-author Rahul Telang, a professor at Carnegie Mellon University, said in a statement. “Weak ties, on the other hand, while they had a greater impact on job leads, have a statistically insignificant impact on job interviews.”

“One possible interpretation is that, for leads to convert into interviews, your connections will most likely be required to conduct follow up on their end, such as make phone calls or provide recommendations,” he continued. “If the connection is weak, these individuals may be less likely to undertake these efforts.”

These findings have implications for businesses and policymakers trying to harness technology most effectively, the authors concluded. “Firms increasingly rely on these networks to find the next employee,” they wrote. “So, it is good to ask going forward: How effective are these networks in finding the right employee, and at what cost?”