Missing the trees for the weekend

If your data looks like this:

A line graph showing noisy data, with the only clear trend being a dip for two every seven data pointsThen, congratulations! You’ve discovered that arcane effect known as “the weekend”. Now go normalize your data, and find out if anything interesting is happening.

I see this anti-pattern happen a lot. What interesting things are we missing because we can’t see past the main effect?

Of course, there is a danger of over-normalizing, and underestimating the impact of the main effect. If you can only afford to staff the help desk five days out of seven, and you’re trying to figure out which days to close your business, then by all means ‘discover’ the weekend…

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