 Let's explore how to find the Z critical value using the Art of Stat web apps So from the website if you scroll down you will find the list of distributions and On there you will find the normal distribution. That's the one we're going to use From here you have three options and we're going to choose the third one find a percentile or quantile Which is basically finding the boundary that's going to cut off a given probability or a given percentage So on here, we're going to leave it at zero and one for the mean and standard deviation since we're looking for a z-score The type of percentile we're going to choose is two-tailed and this is going to allow us to capture the central probability and What do we put in for the central probability? That's going to be our confidence level So if we want to be 95% confident, we're going to leave it at 95 and here we see we get our Bounders 1.96 and negative 1.96 and if we just take the positive version of this, this is our critical value