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.
The average mobile web page uses about 1-Megabyte of data so you could view about 2,000 web pages per month. The average post on Facebook with a photo attachment is about 400-Kilobytes so you could post 5,200 photos per month with a 2-Gigabyte data plan. The average video stream, not HD video, uses about 2-Megabytes per minute so you could watch about 17-hours of a standard video stream per month. The average HD video stream can use as much as 5-Megabytes per minute so you could watch about 7-hours of streaming HD video per month with this plan.