# Are daily updated data a sample or a population?

I want to do some tests based on all historical data of a product updated on a daily basis. These data are not supposed to have any time trend associated with them just be pulled on different days.

I am just wondering if I want to do some statistical inference of this kind of data, do I have to randomly sample it again within this data or I can treat this data as a sample of the whole population (which includes the future data points) if I want to conduct some hypothesis tests?

• What inference do you want to do exactly? – gung Mar 2 '15 at 23:57
• I actually want to compare proportions across different groups – MYjx Mar 3 '15 at 17:47

Think about flipping a coin, another common introductory example, we don't make a list of every time that coin will be flipped and then randomly choose among them, we just use the next $n$ flips as our sample. Your case is similar.