A clinical psychologist investigated the success of two different therapy programmes for anxiety: Cognitive Behavioural Therapy (CBT) and Stress Inoculation Training (SIT). After a 10-week course, patients' anxiety reduction was classified as either 'Substantial Improvement' or 'Minimal Improvement'. The psychologist wanted to see if there was a significant association between the type of therapy received and the level of improvement. The results are shown in Table 1.
Calculate the chi-squared (χ2\chi^2χ2) value for this data by completing Table 2. Show your calculations and state your final χ2 \chi^2\,χ2 value to 2 decimal places.
| Therapy Type | Substantial Improvement | Minimal Improvement |
|---|---|---|
| CBT | 30 | 10 |
| SIT | 20 | 15 |
| Therapy | Improvement | Observed (OOO) | Expected (EEE) | O−EO-EO−E | (O−E)2(O-E)^2(O−E)2 | (O−E)2/E(O-E)^2/E(O−E)2/E |
|---|---|---|---|---|---|---|
| CBT | Substantial | 30 | 26.7 | |||
| Minimal | 10 | 13.3 | ||||
| SIT | Substantial | 20 | 23.3 | |||
| Minimal | 15 | 11.7 | ||||
| χ2\chi^2χ2 = |
Practise Edexcel A Level Psychology Research methods and skills with exam-style questions for A Level Psychology. 657 questions covering Research methods and skills, matched to the Edexcel A Level Psychology (9PS0) 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.
