Selection bias occurs when the association between exposure and health outcome is different for those who complete a study compared with those who are in the target population. Sources of selection bias. Selective survival and losses to follow-up After enrollment of subjects and collection of baseline data there is
NUMBER OF PUBLIC PHOTOS UPLOADED IN 2013. - 680 million, - 56.7 million per month in average, - 1.86 million per day in average. NUMBER OF PUBLIC PHOTOS UPLOADED IN 2012. - 556 million, - 46.3 million per month in average, - 1.52 million per day in average. NUMBER OF PUBLIC PHOTOS UPLOADED IN 2011. - 575 million, - 47.9 million per month in average, - 1.57 million per day in average.
Percentage-wise, only a small amount of Facebook's user accounts are compromised. The raw numbers are still pretty staggering, though. Odds are, either you or a friend have wound up on the wrong end of a hacked Facebook account. It turns out that this happens far more than you'd probably expect: New official statistics from the social network have revealed that more than 600,000 are hacked on a daily basis. Now, according to the statistics, only 0.06% of the billion-plus account logins that happen every day are compromised. Or, as Sophos so helpfully points out: Put another way, that's more than 600,000 per day - or, if you really like to make your mind melt, one every 140 milliseconds.