1. Descriptive Statistics
Involves computing summary measures and constructing graphs, tables and charts to illustrate those measures

2. Measures of Location Arithmetic Mean or Average; Median; Mode; and
Weighted Average

3. Measures of Variability or Spread
Range;
Variance;
Standard Deviation, and
Coefficient of Variation

4. Measures of Location
Measures of location describe data by providing a central tendency (location) value for the data

5. Arithmetic Mean or Average
Population:
x = (Xi) / N
where:
x = population mean;
Xi = the ith value in the data set;
 = summation symbol; and
N = population size
Sample:
X = (Xi) / n
where:
X = sample mean;
Xi = the ith value in the data set;
 = summation symbol; and
n = sample size

6. Median
The median is the middle observation in data that have been arranged in ascending or descending numerical sequence
Median = (n + 1) / 2 ranked observation
where n = number of observations

7. Mode
The mode is the value in a set of data that appears most frequently

8. Weighted Average
A weighted average is an arithmetic mean for which each value (X) is weighted (W) according to some well-defined criterion
Xw = (XW) / W

9. Measures of Variability or Spread
Measures of variability or spread describe data by indicating the extent of the differences between the values of a data set

10. Range
The range of the data set is the difference between the largest and smallest values in the set
Range = Largest Value - Smallest Value

11. Variance x2 =  ( Xi - x )2 / N for populations
The variance provides a numerical measure of how the data tend to vary around the arithmetic mean
x2 =  ( Xi - x )2 / N for populations
s2 =  ( Xi - X )2 / (n - 1) for samples

12. Standard Deviation
The standard deviation may be thought of as a measure of distance from the mean
STD = SQRT of Variance
Population: Sample:
 = SQRT OF 2 S = SQRT of S2

13. Coefficient of Variation
The coefficient of variation is a measure of relative variation
Population: Sample:
V = ( / x ) * 100 V = ( S / X ) * 100
where:
V = Coefficient of Variation