Summary
Cumulative frequency is a method used to find the running total of frequencies up to a certain point in grouped data. It helps in estimating the median and interquartile range by plotting cumulative frequency curves.
Exam Tips
Key Definitions to Remember
- Cumulative Frequency — The total of the frequencies up to a particular value.
- Interquartile Range (IQR) — The difference between the upper quartile (Q3) and the lower quartile (Q1).
Common Confusions
- Confusing cumulative frequency with simple frequency.
- Misinterpreting the axes on a cumulative frequency graph.
Typical Exam Questions
- How do you find the median from a cumulative frequency graph? Draw a horizontal line at 50% of the total frequency and drop it to the x-axis.
- What is the interquartile range? Subtract Q1 from Q3.
- How do you plot a cumulative frequency curve? Use the upper boundary of each group on the x-axis and cumulative frequency on the y-axis.
What Examiners Usually Test
- Ability to construct and interpret cumulative frequency tables and graphs.
- Estimating median and quartiles from cumulative frequency curves.