I am having trouble understanding Z- Score. I attempt to do the information as it is presented however, I always seem to not get the proper results. Below are some examples. To my understanding the mean is 448 grams. The SD is 10.2 and the X is represented as 451. I end up with (-.2941) However, I have been informed that is wrong. What am I missing?

Z= X - (the mean) / standard deviation.

A jar of peanut butter contains 451 grams with a standard deviation of 10.2 grams. Assuming a normal distribution, nd the probability that a jar contains less than 443 grams. \f