How to Calculate Z-score of Binomial Test?


I would like to ask how to calculate the z-score of a Binomial test? I am using this link as a reference.

I don't get its assumption (second sentence of step 2). I've searched about the formula for this but still I don't get it. I don't know where I can get the mean value. I got X = 26, n = 30. z = (X-u)/n

Please help me. I'm trying to make my own one-tailed binomial test. (Or the equivalent of one-tailed test in the link I've given above is just the removal of negative critical region???)


New Member
the +/-2.3263 come from a z-table, like the one linked at the top of this forum (Normal Table)

the "critical region" is the rejection region. That is, if the z-value is in that region then reject H0
I need to look for the value of the confidence level which is 0.99 in the normal table then add the values of the rightmost column and uppermost row to get the +/-2.3263. Am I correct??