The mean of a set of test scores is 50, and the standard deviation is 5. For a raw score of 55, the corresponding z score is +1. What's the z score when the standard deviation is half as much, or 2.5? From this example, what can you conclude is the effect of decreasing the amount of variability in a set of scores on a standard score (given all else is equal, such as the same raw score), and why is this effect important?