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.
Here's how much time people spend on Facebook per day. Facebook's more than 1.44 billion monthly active users around the world spend an average of 20+ minutes per day on the social network, liking, commenting, and scrolling through status updates, according to analysts from Needham, citing comScore data. That accounts for nearly 20% of all time online.