An environmental scientist is researching the potential correlation between the distance from a major highway (in meters) and the soil concentration of nitrogen dioxide (NO2\text{NO}_2NO2, in μg/m3\mu\text{g/m}^3μg/m3). Soil core samples were collected from a sample of 17 distinct locations.
An extract from the table of critical values for Spearman's ranked correlation coefficient (rsr_srs) is shown below.
| Level of significance for a two-tailed test | ||||
|---|---|---|---|---|
| 0.10 | 0.05 | 0.02 | 0.01 | |
| n=4n = 4n=4 | 1.000 | |||
| 5 | 0.900 | 1.000 | 1.000 | |
| 6 | 0.829 | 0.886 | 0.943 | 1.000 |
| 7 | 0.714 | 0.786 | 0.893 | 0.929 |
| 8 | 0.643 | 0.738 | 0.833 | 0.881 |
| 9 | 0.600 | 0.700 | 0.783 | 0.833 |
| 10 | 0.564 | 0.648 | 0.745 | 0.794 |
| 11 | 0.536 | 0.618 | 0.709 | 0.755 |
| 12 | 0.503 | 0.587 | 0.671 | 0.727 |
| 13 | 0.484 | 0.560 | 0.648 | 0.703 |
| 14 | 0.464 | 0.538 | 0.622 | 0.675 |
| 15 | 0.443 | 0.521 | 0.604 | 0.654 |
| 16 | 0.429 | 0.503 | 0.582 | 0.635 |
| 17 | 0.414 | 0.485 | 0.566 | 0.615 |
| 18 | 0.401 | 0.472 | 0.550 | 0.600 |
| 19 | 0.391 | 0.460 | 0.535 | 0.584 |
| 20 | 0.380 | 0.447 | 0.520 | 0.570 |
rs r_s\,rs must equal or exceed the table critical value to be significant at the stated level of probability.
Using this table, identify the critical value at the 2% (0.02) level of significance for a two-tailed test for the data collected in this study.
513 exam-style questions on OCR A Level Psychology Data recording, analysis and presentation. Each one has a worked solution and a mark scheme showing where the marks go.