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Thanks a lot Pahtsan for trying it out and for leaving an excellent feedback!
I guess my idea was that we would try the formula with the pen and paper and then refer to the app to compare the results. Or when we are on the go (e.g. on the bus to work) we look at the formula, enter the numbers and see the variables substituted in the formula. I may consider providing an option to disable the calculator fields so you’re not tempted to use it 🙂 If I do an update, I’ll also include the Covariance formula.
Thanks again and good luck with the exam!