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.
Whereas Facebook today is the number one social media site, MySpace languishes in near-obscurity as a shadow of its former self â a victim of bad decision-making from its leadership. Today, just 50 million people even visit MySpace per month, and while that may not seem like a small number, compare that to how many people visit Facebook each month: 1.44 billion users, as of March 31, 2015.