Answer:
A z score must be negative (-) whenever it is located on the left half of the normal distribution. This is because the left half of the normal distribution represents scores that are below the average (mean) of the distribution. A z score is a standard score that tells us how many standard deviations a particular score is from the mean. Thus, a negative z score indicates that the corresponding score is located below the mean of the distribution by a certain number of standard deviations. In contrast, a positive z score indicates that the corresponding score is located above the mean of the distribution by a certain number of standard deviations.