Approximately 68% (68.26%) of the data items fall within one standard deviation of the mean.Refer to Figure 2 for the visual representation of the 68 – 95 – 99.7 Rule. We have seen that the standard deviation plays an important role in the normal distribution. The area under the curve represents 100% (or 1.00) of the data (or population) and the mean score is 0. The normal curve, also called a bell-shaped curve, is represented in Figure 1. This section will explore how to determine this.Ĭonsider the normal curve which is an idealized representation of a normally distributed population. As an example, a student who has written a college entrance exam may want to know where they placed in comparison to all other students. We will shift gears and explore how to determine where a specific data value lies in relation to all other values. When a set of data values is normally distributed, the 68-95-99.7 Rule can be used to determine the percentage of values that lie one, two or three standard deviations from the mean. Solve applications using z-score tables.By the end of this section it is expected that you will be able to:
