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Can anyone explain how normal distribution works? Apparently it has to be symmetrical and also I have heard that a lot of dataare "normally distributed" like weight and test scores.

How can this happen? Doesn't that assume that 50% of all samples are above the mean and 50% are under? I just don't see how any collection of data can be symmetrical in this way unless it's specifically picked to fit into this model.

How can this happen? Doesn't that assume that 50% of all samples are above the mean and 50% are under? I just don't see how any collection of data can be symmetrical in this way unless it's specifically picked to fit into this model.