## Re: Simply way to calcuatle p value ?

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Reply #1 –

The "simplest way" is, arguably, to enter the figures into an online calculator: https://www.google.com/search?q=binomial+test+calculator

The null hypothesis of wild guessing would be a probability = 1/2 each time, since you have two alternatives A and B. What you are looking for, is the chance of getting "such a wild result" as *10 or more*, if the null hypothesis is true.

If you want to do it by hand: Then https://en.wikipedia.org/wiki/Binomial_distribution#Cumulative_distribution_function .

Rather than calculating up to 10, you can calculate "from 10 and up": since probabilities are 1/2 The chance of getting 10 or 11 or 12, equals the chance of getting 2 or 1 or 0. The probability of 1/2 simplifies p^k(1-p)^{n-k} to 1/2^n.