For scientific data I would start by making sure you understand these and then try to apply them:
https://en.wikipedia.org/wiki/Standard_deviation
https://en.wikipedia.org/wiki/Margin_of_error
http://www.mathsisfun.com/data/standard-deviation.html
If you're really curious grab all the data you can and start breaking it down. Look for patterns. Find out what is really going on. Compare trends based on day of the week, day of the month, season, etc.
As far as art I remember talk here about sales coinciding with the phase of the moon. Actually I wouldn't be surprised to see some kind of correlation at all!
