25.2 Cumulative frequency — Practise with help
Warm-up: remember
- Find the median of .
- Add frequencies .
Feedback
- . 2. .
Practise with help
Use this table: classes , , have frequencies .
1. Find the cumulative frequency at each upper boundary.
Hint
Keep a running total, starting from the first frequency.
Step
The totals are , then , then .
Full working
The cumulative frequencies are .
2. State the coordinates to plot, including the starting point.
Hint
Pair each upper boundary with its cumulative frequency.
Step
Start at , then use boundaries .
Full working
Plot , then draw a smooth increasing curve.
3. Earlier work: the frequencies are . Which class has the greatest frequency?
Hint
Compare the three frequencies, not their running totals.
Step
The largest frequency is .
Full working
The class has the greatest frequency, .