- The count in any given interval.
- proportion of weight in each interval.
- e.g the frequency divided by the total number of X.
- Each bar covers an interval & is centered at the midpoint.
- The bars height is the number of data points in the interval.
- Same as the histogram but the vertical axis represents relative frequency
- Divide the data into equal groups & see how far apart the extreme groups are.
- Q1 is the median of the lows / Q3 is the median of the highs