The data set smokers.rda contains the time to fracture healing (in weeks) of patients who presented with a tibial fracture (variable ‘Time’). Smokers and non-smokers are indicated in the variable ‘Group’ (nominal data).
smokers
Patient Group Time
1 1 Smoker 10
2 2 Smoker 11
3 3 Smoker 11
4 4 Smoker 12
5 5 Smoker 15
6 6 Smoker 17
7 7 Smoker 17
8 8 Smoker 18
9 9 Smoker 18
10 10 Smoker 19
11 11 Smoker 22
12 12 Smoker 24
13 13 Non Smoker 10
14 14 Non Smoker 10
15 15 Non Smoker 11
16 16 Non Smoker 12
17 17 Non Smoker 15
18 18 Non Smoker 15
19 19 Non Smoker 16
20 20 Non Smoker 17
- Using the sign test and <=16 weeks as ‘cut off’ point; is fracture healing significantly delayed in patients who smoke (significant when p < 5%)?
- Using the Chi Square test and the same ‘cut off’ point’, is there a statistically significant difference? (significant when p < 5%). The Chi Square distribution table is shown below:
| Degrees of Freedom | 10% | 5% | 1% |
|---|---|---|---|
| 1 | 2.71 | 3.84 | 6.63 |
| 2 | 4.61 | 5.99 | 9.21 |
| 3 | 6.25 | 7.81 | 11.34 |
| 4 | 7.78 | 9.49 | 13.28 |
| 5 | 9.24 | 11.07 | 15.09 |
| 10 | 15.99 | 18.31 | 23.21 |
The value of radioisotope bone scanning in the diagnosis of multiple myeloma is being evaluated. 50 consecutive patients with suspected multiple myeloma and a high erythrocyte sedimentation rate (ESR) were identified. The ESR was consider high if is was more than 10 mm per hour. All 50 patients had a radioisotope bone scan. Ten patients had a positive bone scan, showing one or more areas of increased uptake of radioisotope. In 36 of the 50 patients the diagnosis of multiple myeloma was made following bone marrow aspiration. Six of these patients had a positive bone scan.
- Calculate the following parameters: True Positives, True Negatives, False Positives, False Negatives, Positive Predictive Value, Negative Predictive Vale, Sensitivity, Specificity, Accuracy