Z-scores can be looked up in a Z-Table of Standard Normal Distribution, in order to find the area under the standard normal curve, between a score and the mean, between two scores, or above or below a score. Likewise, it does not make sense to compare scores from two different samples that have different means and standard deviations. It would not make sense to compare apples and oranges.
Z-scores allow for comparison of scores, occurring in different data sets, with different means and standard deviations. A z-score indicates the number of standard deviation a score falls above or below the mean. It represents a distribution of standardized scores, called z-scores, as opposed to raw scores (the actual data values).
The standardized normal distribution is a type of normal distribution, with a mean of 0 and standard deviation of 1.
