The partially completed histogram and the partially completed table below show the times taken, to the nearest second, by a group of people to complete a puzzle. The two bars shown are drawn accurately, and the vertical axis has no scale marked on it.
| Time (seconds) | Frequency |
|---|---|
| 1–4 | 2 |
| 5–8 | 12 |
| 9–10 | 8 |
| 11–15 | |
| 16–20 | 3 |
Complete the table.
Find the heights, in terms of frequency density, of the three bars that are missing from the histogram.
One of the participants is selected at random. Estimate the probability that this participant completed the puzzle in under 10 seconds.
244 exam-style questions on AQA A Level Maths 2.2 L: Data presentation and interpretation, covering 2.2.1 Single-variable data diagrams, 2.2.2 Scatter diagrams and correlation, 2.2.3 Central tendency, variation and standard deviation, 2.2.4 Outliers and cleaning data, and 2.2 L: Data presentation and interpretation. Each one has a worked solution and a mark scheme showing where the marks go.