✔ CF stands for Cumulative Frequency which is the running total.
Q2. Which X-axis value do we plot?
✔ Ogives are plotted using the upper class limits on the horizontal axis.
Q3. If N is 50, where is median?
✔ The median position in a cumulative frequency graph is found at N divided by two.
Show transcript
[Slide 1] Understanding Cumulative Frequency
This graph tracks the running total of students or items as we move up categories. It helps us see where the middle value lies easily without complex calculations.
[Slide 2] How to Construct the Graph
First, make a table adding previous frequencies to the current one. Then plot these totals against the upper boundary of each class interval.
[Slide 3] Worked Example Table Setup
Let's say five students scored between zero and ten marks. The next group has five more, so the cumulative total is now ten.
[Slide 4] Worked Example Coordinates
We plot the upper limit ten with height five. Then we plot twenty with height ten and connect them smoothly to form the ogive.
[Slide 5] Avoiding Common Errors
Students often plot the lower limit or forget to add the previous frequency. Remember, always use upper limits and running totals.
[Slide 6] Key Takeaways Summary
To summarize, add frequencies cumulatively and plot against upper limits. This graph helps you find the median quickly for exams.