A psychologist investigated the relationship between the number of hours of physical exercise per week and self-reported wellness scores. She obtained a sample of 18 participants (N=18N = 18N=18) and calculated Spearman's rank correlation coefficient (rsr_srs). Her calculated value was rs=0.612r_s = 0.612rs=0.612.
She concluded that there was a significant positive correlation and rejected her null hypothesis.
Table 1: Critical values for Spearman’s Rho (rsr_srs)
| NNN | Significance level (two-tailed) | |
|---|---|---|
| 0.05 | 0.01 | |
| 15 | 0.521 | 0.661 |
| 16 | 0.503 | 0.635 |
| 17 | 0.485 | 0.615 |
| 18 | 0.472 | 0.597 |
| 19 | 0.460 | 0.582 |
Note: To achieve significance, the calculated value of rs r_s\,rs must be equal to or greater than the critical value in the table.
What is meant by a 'Type 1 error'? Explain why the psychologist thought that she had not made a Type 1 error.
Practise AQA A Level Psychology Inferential testing (A-level only) with exam-style questions for A Level Psychology. 123 questions, matched to the AQA A Level Psychology (7182) specification and written in Paper 1, Paper 2 and Paper 3 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.
