math
posted by sam .
Find the zscore for the given raw score, mean, and standard deviation. Assume a normal probability distribution
score = 15, ì = 16 , and ó = 2
Could you show me how to do this. My instructor has tried but I just don't understand how to do it and I have several questions to answer that are just like this.

z = (xu)/s, where x is the value, u is the mean, and s is the standard deviation.
You have x = 15, u = 16, and s = 2. z =? 
but wouldn't that make it a negative?

You can have a negative z score.

So anytime it is asking for a z score this is the formula to use? What if it was not normal distribution? Is their another formula?
Thank you for your help. I wish my instructor explained it that easy! 
Z scores are used for finding probabilities with normal distributions.
If you cannot assume the distribution is normal, a z score would not be used.