A researcher records the reaction times of 140 participants. The results are shown below.
| Reaction time (s) | Frequency |
|---|---|
| 0.20 | 5 |
| 0.25 | 15 |
| 0.30 | 30 |
| 0.35 | 40 |
| 0.40 | 30 |
| 0.45 | 15 |
| 0.50 | 5 |
Which conclusion about the distribution of these reaction times is correct?
It is a skewed distribution, because the peak at 0.35 s is not at the centre of the 0.20 s to 0.50 s range.
It is a normal distribution, because the frequencies rise to a single peak at 0.35 s and fall away evenly on each side.
It is a normal distribution, and its mode is 40, because 40 participants share the most common reaction time.
It is a skewed distribution, because most of the participants took 0.30 s or longer to react.
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.