A tap is filling a bath. Every minute you check how much water is in it.
Can the amount ever go down? Why?
No: water is only ever added
- Cumulative frequency
- A running total of the frequencies.
| Time (seconds) | Frequency | Cumulative frequency |
|---|
| 0 < t ≤ 10 | 5 | |
| 10 < t ≤ 20 | 8 | |
| 20 < t ≤ 30 | 7 | |
The cumulative frequencies are 5, 14 and 26.
What is the frequency of the last class?
12
The ages of the people at a party. Work out the cumulative frequency for
| Age (years) | Frequency |
|---|
| 0 < a ≤ 10 | 8 |
| 10 < a ≤ 20 | 15 |
| 20 < a ≤ 30 | 20 |
| 30 < a ≤ 40 | 12 |
| 40 < a ≤ 50 | 5 |
0 < a ≤ 10
8
10 < a ≤ 20
23
20 < a ≤ 30
43
30 < a ≤ 40
55
40 < a ≤ 50
60
| Mass (kg) | Frequency | Cumulative frequency |
|---|
| 0 < m ≤ 20 | 5 | 5 |
| 20 < m ≤ 40 | 12 | 17 |
| 40 < m ≤ 60 | 15 | 32 |
| 60 < m ≤ 80 | 8 | 40 |
| Height (cm) | Frequency | Cumulative frequency |
|---|
| 140 < h ≤ 150 | 6 | |
| 150 < h ≤ 160 | 14 | |
| 160 < h ≤ 170 | 16 | |
| 170 < h ≤ 180 | 4 | |
| Mass (kg) | Frequency | Cumulative frequency |
|---|
| 0 < m ≤ 20 | 5 | |
| 20 < m ≤ 40 | 12 | |
| 40 < m ≤ 60 | 15 | |
| 60 < m ≤ 80 | 8 | |
| Mark | Frequency | Cumulative frequency |
|---|
| 0 < m ≤ 10 | 3 | 3 |
| 10 < m ≤ 20 | 9 | 12 |
| 20 < m ≤ 30 | 13 | 25 |
| 30 < m ≤ 40 | 5 | 30 |
The cumulative frequencies for five classes are 7, 19, 34, 46 and 50. Work out the five frequencies.
7, 12, 15, 12, 4
Leo plots each point at the middle of its class. Why is this wrong?
The total is only reached at the top of the class
Complete the cumulative frequency column of the table.
3, 12, 26, 32
Which point is plotted for the class 20 < t ≤ 30 in question 1?
(30, 26)
The cumulative frequencies of four classes are 5, 13, 29 and 36. Find the frequency of the third class.
16
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