Question 17:

Asked on October 29, 2007

Tags: Z-Score , Unusual Event

1

Answer:

No answer provided yet.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.