A z-score tells you how many standard deviations your score is away from the mean. If z is positive, your score is above the mean. If z is negative, your score is below the mean. If your score is at the mean, z = 0.
Take your score (X) and subtract the mean from it. X with a bar over it is the symbol for the mean, and it’s pronounced bar-x (like the ranch on an old cowboy movie).
Divide the result of your subtraction by the standard deviation.
Takes it. It’s easier than mixing muffins, and there’s no preheating the oven. 🙂