Facebook's chief operating officer, Sheryl Sandberg, famously called on women to "lean in" in the workplace and in their personal lives. The business leader, reportedly worth somewhere between $400 million and $1 billion depending on who you read, probably didn't know how this would be parlayed into a study about WTA and ATP pros and how they challenge line calls in matches. But that's just what Jon Wertheim at Sports Illustrated set out to show, noting that male pros object officially to calls more than their female peers, among other statistics compiled by the Scorecasting scribe. And Slate.com has some statements about the findings, as does discriminating SI reader and letter writer "Dane."

What's interesting is how male and female tennis players are correct in their challenges basically the same percentage of the time, even if the WTA's pros don't challenge as often. So are the women better at it? Are they more easily swayed away from challenging by chair umpires with whom they often inquire first? What do you make of all these numbers?

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