1. Descriptive Statistics: Describing Data

2. Measures of Center
Mean or Arithmetic Mean: add up the values of the observations; then divide by the number of observations.
Median: the value for which half of the observations are above that value & half are below it.
Mode: Most common, most frequent, or most probable value.

3. Measures of Spread
Range – difference between highest and lowest values
Take maximum value and subtract minimum
Mean Absolute Deviation (MAD) – the distance of each point from the mean
-Find the mean
Find the distance of each value from the mean
Average those distances

4. Shapes of Distribution
Normal – symmetrical shape
-For a normal distribution, the left and right sides are mirror images of each other.
-The mean, median, and mode are the same.
Skewed – not symmetrical; more values on one side
-For a skewed distribution, the left and right sides are uneven
-The mean, median, and mode are not the same.
-Skewed to the left – longer lines on left side (mean is smaller than median)
-Skewed to the right – longer lines on right side (mean is larger than median)