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.
Of those, 1.25 billion were mobile users, an increase of 24 percent year over year. Facebook also shared that it now has 936 million daily active users (a 17 percent bump year over year) and 798 million mobile daily active users (a 31 percent increase year over year). This means about 65 percent of Facebookâs members use the service daily, and 64 percent of its mobile members use it daily on mobile.