Everything else is ready: study the parts, the key terms and the quiz below.
The CDF, Percentiles and Quantiles
Read the fraction of data below any value, and the value below any fraction.
In this lesson6 parts
- 01From one threshold to any threshold
- 02Build the empirical cumulative distribution
- 03Read a fraction at a chosen duration
- 04Read a duration at a chosen fraction
- 05A whole minute is a separate decision
- 06Reproduce the reading and test another fraction
Key terms
The words this lesson introduces, each in one line. The module’s glossary collects them all.
- rank
- An observation's position after sorting, starting at 1 for the smallest. Tied values still get separate ranks.
- CDF
- Cumulative probability at or below a value.
- empirical CDF
- The observed fraction at or below a value. It steps up by
1 / nat each observation and is flat between them. - cumulative fraction
- The count at or below a value divided by all selected observations.
- quantile
- The value at a chosen cumulative fraction.
- percentile
- A quantile whose fraction is written as a percentage: the 90th percentile is the 0.9 quantile. (narration)
- quartiles
- Quantiles at 25%, 50% and 75%.
Quiz 5 questions
Your first pick on each question is the one that counts, and a right one earns a coin. Getting one wrong here is how the lesson sticks.
Practice
Problems to solve in your own notebook. Each states the problem, not the steps: working out the steps is the exercise. Level A applies the lesson, B combines it with earlier ones, C stretches it.
The self-checking notebook for this lesson is Histograms, density and the ECDF.
Common mistakes
What you will see when it goes wrong, why it happens, and the fix.
Where it’s used
Where this lesson’s ideas turn up in real work.