A psychologist records the number of landmarks recalled, out of 20, by five participants after they practise a route. Before practice, the group's mean was 9 landmarks.
| Participant | Landmarks recalled after practice |
|---|---|
| A | 9 |
| B | 11 |
| C | 12 |
| D | 13 |
| E | 15 |
Calculate the percentage increase in the mean number of landmarks recalled from before practice to after practice. Give your answer to one decimal place. Show your working.
173 exam-style questions on OCR GCSE Psychology 7.3 Analysing Research, covering 7.3.1 Types of Data, 7.3.2 Measures of central tendency, 7.3.3 Other descriptive statistics, 7.3.4 Tables, Charts and Graphs, 7.3.5 Reliability, 7.3.6 Validity and effects on validity, and 7.3.7 Sources of bias. Each one has a worked solution and a mark scheme showing where the marks go.