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.
According to the official Facebook statistics page (http://www.facebook.com/press/in...), Facebook users spend 700 billion minutes per month on Facebook. At 500 million active users, this equates to 1400 minutes per user per month. So over the course of a 30 day month, the average user spends approximately 46 minutes per day on Facebook.