Cumulative Frequency and Percentiles
Use cumulative frequency curves to estimate medians, quartiles, percentiles and proportions.
What cumulative frequency shows
Cumulative frequency counts how many values are less than or equal to an upper class boundary.
Quartiles
For \(n\) data values, estimate:
- Lower quartile near position \(\frac n4\)
- Median near position \(\frac n2\)
- Upper quartile near position \(\frac{3n}4\)
The interquartile range is \(Q_3-Q_1\).