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.
Ask a Question. Friends. Why do certain friends seem to show up as one of the the six photos in the small friends list photo box at the top of Facebook Timeline?Are these the 6 friends people who have visited your profile recently or have been online recently?riends. Why do certain friends seem to show up as one of the the six photos in the small friends list photo box at the top of Facebook Timeline?