Characteristics of the Normal Curve

• MEAN = MEDIAN = Mode: The mean and the median are the same and are located in the center of the curve. 50% of the data is above or below and the z score is 0

• Unimodal, Symmetric, bell-shaped

• The "Area" under the curve is 1.

Area Under the Curve???

• The total area under the curve is 1.

• The percent of the data also determines the probability of getting a number in that section.

Lets look at the table

The table shows you what the area looks like for a Normal Curve with the mean = 50 and SD = 5

The Empirical Rule 68%, 95%, 99.7%

• 68% of the data is within 1 SD of the mean above and below.

• 95% of the data is within 2 SD of the mean above and below.

• 99.7% of the data is within 3 SD of the mean above and below.

Finding Probabilities with the Empirical Rule

• Use the diagram to help! Mean is 80 and the SD is 10

• What percent of the data lies between 70 and 80? (0.34 or 34%)

• What percent of the data lies between 90 and 110? (0.135+0.0235 = 0.1585 or 15.85%)