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.
In addition, Facebook says it had 751 million monthly active mobile users in the first quarter, up 10 percent from 680 million in the fourth quarter of 2012. Here is a look at how the number of active users at Facebook has grown: 1 million â End of 2004. 5.5 million â End of 2005. 12 million â End of 2006.