| Question : Having obtained the z score and then derived the percentage... what does the percentage tell you? Answer : The percentage tells you how much area is above or below that point on a normal curve. That by itself doesn’t help much of course. The percent of area tells you how unusual an event is. For example, if you knew that the z-score of someone’s test was a z of 2.5, this percentage tells you that score is in the 99th percentile. In other words it’s a very high score, and an unusual event. Usual events will fall closer to 50%. In fact the properties of the normal curve dictate that 68% of the values will fall within 1 standard deviation (plus and minus) of the mean. In other words, if test scores were normally distributed, about 70% of the test takers will fall within 1 standard deviation of the average. | How helpful was this answer?
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