2. What is a Density Curve?
• A smooth curve that can be drawn over a
histogram if you have a large number of
observations
• It is above the x-axis and the area
between the curve and the x-axis its area
is always 1
• These “curves” may be straight lines
• A Uniform Density Curve looks like a
rectangle
3. Normal Distribution
• Normal Distribution - data that fits a
normal (bell shaped) curve
• We can utilize a z-score formula to help
determine the population mean, standard
deviation or the z-score if you have a
sample mean or one piece of data
• We can also utilize a z-score to find the
percentile ranking of a piece of data
4. 68-95-99.7 Rule
If data is Normal the 68-95-99.7 Rule
applies
This rule states that
68% of the data fall within 1 standard
deviation
95% of the data fall within 2 standard
deviations
99.7% of the data fall within 3 standard
deviations
