Handling Data 6
3 marks · NormalThe table shows the time (in minutes) spent online by a group of students one evening.
| Time (minutes) | Frequency |
|---|---|
| 0 < t \leq 10 | 4 |
| 10 < t \leq 20 | 16 |
| 20 < t \leq 40 | 20 |
The first bar on the corresponding histogram has a width of 10 units and a height of 0.4. Work out the frequency density for each group and use them to find the height of the second bar.
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The height of the second bar should be 1.6 (±0.02)
Common mistakes: Using frequency instead of frequency density; Forgetting to divide by the correct class width
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Marking points
M1 · 1 mark · Correctly recalls or uses the formula frequency density = frequency / class width
A1 · 1 mark · Finds the correct class width for 10 < t ≤ 20 is 10; frequency is 16.
A2 · 1 mark · Correctly calculates height as 16 / 10 = 1.6
Worked solution
Frequency density = frequency ÷ class width
For 10 < t ≤ 20: frequency = 16, class width = 10
Frequency density = 16 ÷ 10 = 1.6