Final answer:
According to the empirical rule, about 68% of the data in a normal distribution is within one standard deviation of the mean, which corresponds to z-scores between -1 and 1.
Step-by-step explanation:
The question is about the percentage of data found within certain ranges of standard deviations from the mean in a normal distribution, as represented by z-scores. Specifically, it refers to the proportion of data within one standard deviation (z-scores between -1 and 1). According to the empirical rule (also known as the 68-95-99.7 rule), about 68% of the data in a normal distribution is within one standard deviation of the mean.
So, about 68% of the area is between z=-1 and z=1 (or within 1 standard deviation of the mean). This empirical rule is a quick way to estimate the spread of data in a normal distribution and is useful for various statistical analyses.